[CLS] the convergence of nanoscience and drug delivery has prompted the formation of the field of nanomedicine , one that exploits the novel physicochemical and biological properties of nanostructures for improved medical treatments and reduced side effects . [SEP]

[CLS] until recently , this nanostructure - mediated strategy considered the drug to be solely a biologically active compound to be delivered , and its potential as a molecular building unit remained largely unexplored . [SEP]

[CLS] a growing trend within nanomedicine has been the use of drug molecules to build well - defined nanostructures of various sizes and shapes . [SEP]

[CLS] this strategy allows for the creation of self - delivering supramolecular nanomedicines containing a high and fixed drug content . [SEP]

[CLS] through rational design of the number and type of the drug incorporated , the resulting nanostructures can be tailored to assume various morphologies ( e . g . nanospheres B-nanoparticle , rods , nanofibers B-nanoparticle , or nanotubes B-nanoparticle ) for a particular mode of administration such as systemic , topical , and local delivery . [SEP]

[CLS] this review covers the recent advances in this rapidly developing field , with the aim of providing an in - depth evaluation of the exciting opportunities that this new field could create to improve the current clinical practice of nanomedicine . [SEP]

[CLS] the construction of complex supramolecular architectures through the self - assembly of basic molecular building blocks is a strategy that can be both practical and inspiring , affording nanostructures with properties that the individual unit does not necessarily possess . [SEP]

[CLS] nature leads the way in harnessing the power of molecular assembly , as exemplified by the folding of polypeptide B-material chains I-material into functional proteins B-material 2 capable of specifically recognizing important biomolecules and mediating many biological events , forming the dynamic cytoskeletons from tubulins and actins essential for cellular and subcellular functions , and creating hair , nails , hooves and horns from the multilevel assembly of keratin proteins B-material . [SEP]

[CLS] inspired by these exquisite assembly systems , the accumulated knowledge from over fifty years of research has enabled the creation of a wide range of supramolecular structures from an ever expanding set of natural and synthetic building blocks , including small synthetic molecules , block copolymers , rationally designed peptides B-material , carbohydrates B-material , proteins B-material and dna . [SEP]

[CLS] concurrently , functional utilization of these supramolecular nanostructures has been extensively explored in diverse areas , particularly in the context of drug delivery . [SEP]

[CLS] the control over the size , morphology , surface chemistry , internal structures , and stability ( including both disassembly kinetics and pathways ) of supramolecular nanostructures bestows the potential to carry , protect and release a therapeutic cargo in a highly regulated manner . [SEP]

[CLS] this carrier - cargo relationship is one based on a separation of function , however , with the molecular building blocks purely responsible for delivery ( assuming biocompatibility B-property and inertness ) and the drug for the ensuing bioactivity . [SEP]

[CLS] once its function has been fulfilled the carrier is considered waste material B-material that needs to be cleared . [SEP]

[CLS] an emerging approach for the delivery of therapeutic agents has been to consider the drug itself as a key component of the self - assembly possessing the potential to create its own nanostructures . [SEP]

[CLS] in this way , extraneous materials can be avoided without loss of function , perhaps leading to more effective therapies due to the increased drug loading , elimination of the leakage issue associated with encapsulated drugs , and the reduced need to remove synthetic carrier material B-material . [SEP]

[CLS] what is unclear is the extent to which the potential intermolecular B-property interactions I-property afforded by a drug ' s molecular structure can be harnessed to allow the rational design of a particular nanostructure and how general this approach can truly be given the wide range of structural types in clinical use . [SEP]

[CLS] this review will discuss a number of strategies that have been adopted in which small molecule drugs have been utilized as building blocks in the construction of their own nanostructures , with an emphasis on those that involve true self - assembly pathways . [SEP]

[CLS] in this context , molecular assembly is interpreted as the spontaneous and reversible association of molecules into aggregates ( e . g . molecular clusters , discrete morphologies , or three dimensional networks ) in order to minimize system free energy . [SEP]

[CLS] it is important to note that nanostructures created through molecular selfassembly are distinct from those prepared by precipitation or emulsion methods in that the physiochemical properties of the former ( e . g . size , shape , internal order , stability , aggregation number , surface chemistry ) are reflective of the molecular characteristics of the building units and the assembly conditions . [SEP]

[CLS] it is the interplay of the systemic entropy with the enthalpic interactions among the building units , water B-material , and other molecules present in the assembly system that defines the eventual self - assembled morphology . [SEP]

[CLS] we believe that the rapidly growing area of drug - promoted molecular assembly holds great promise for future research in nanomedicine and cancer chemotherapy , harnessing the intrinsic molecular interactions of a drug to build its own nanocarrier that , to paraphrase lehn ' s definition of supramolecular chemistry , provides " functions beyond the drug " . [SEP]

[CLS] small molecule drugs exhibit a wide range of chemical structures that determine how their solubility B-property , aggregation , and transportation behavior in solution ultimately determine their pharmacokinetic profiles after administration and pharmacodynamics in interfacing with their biological targets . [SEP]

[CLS] large hydrophobic B-property moieties , such as hydrocarbons or polyaromatic segments that possess strong selfassociative interactions , can lead to solubility B-property problems and a high propensity for self - aggregation in aqueous solution , whereas a number of charged groups , e . g . carboxylates B-material or amines B-material , bestow a greater solubility B-property and reduce the potential for self - association . [SEP]

[CLS] the study of the self - association behavior of drug molecules and potential candidates is an important subject in pharmaceutical research . [SEP]

[CLS] knowledge of how these molecules interact with themselves will aid in improving their efficacy , in understanding their pharmacokinetic profile , and in developing the most suitable formulation for administration . [SEP]

[CLS] for example , shoichet and coworkers investigated the aggregation behavior of seven hydrophobic B-property anticancer B-property drugs and found that the formation of colloidal particles inhibited the in vitro cytotoxic B-property potential . [SEP]

[CLS] these colloidal structures could be disrupted in the presence of surfactants B-property , restoring the respective drug ' s toxicity B-property . [SEP]

[CLS] it was also found that the colloidal forms exhibited greater interactions with proteins B-material , such as albumin , causing unpredictable pharmacokinetic behavior . [SEP]

[CLS] drugs that are amphiphilic B-property , containing well separated large hydrophobic B-property and charged groups , could demonstrate reversible self - assembly behavior , resulting in formation of dynamic molecular clusters or even discrete supramolecular nanostructures of well - defined size and shape . [SEP]

[CLS] for example , anthracyclines B-material , a class of antibiotic - based antineoplastics characterized by a hydrophobic B-property planar anthraquinone moiety and a hydrophilic B-property amino - sugar ring ( fig . 1 ) , possess decent aqueous solubility B-property due to the ionizable B-property amine B-material group I-material and are commonly observed to exist as dimers and higher oligomers in solution . [SEP]

[CLS] studies suggest that these dimers exist in parallel and antiparallel orientations of the molecules . [SEP]

[CLS] it has been postulated that the structural differences in the packing among the various derivatives , e . g . daunomycin , adriamycin ( doxorubicin B-material ) , 4 ' - epiadriamycin , may account for the variation in pharmacological activity . [SEP]

[CLS] hayakawa and coworkers have also reported the formation of doxorubicinbased hydrogels through the use of high nacl concentrations , which induce further self - association via - stacking of the aggregates . [SEP]

[CLS] similar dimerization behavior was also found for the anthracyclinealternative mitoxantrone , and for the water B-property - I-property soluble I-property camptothecin derivative irinotecan ( cpt - 11 ) . [SEP]

[CLS] folic B-material acid I-material , also known as vitamin m or b9 , is another example that illustrates a drugs ' self - assembling potential . [SEP]

[CLS] the pterin ring is a critical feature of folic B-material acid I-material ' s self - assembly as its nitrogen B-material and oxygen B-material atoms I-material are arranged in such a fashion as to allow the formation of a particular arrangement of hydrogen B-material bonds , similar to that of nucleic B-material acids I-material in dna . [SEP]

[CLS] in alkaline solution , the self - association of folic B-material acid I-material proceeds via the formation of hoogsteen - bonded tetrameric discs , which then stack through - interactions and inter - disc hydrogen B-material bonding to form chiral columns . [SEP]

[CLS] further ordering results in liquid - crystalline mesophases , the nature of which can be influenced by folate concentration and the addition of salts B-material . [SEP]

[CLS] cui and coworkers recently found that the assembly of folic B-material acid I-material could be manipulated into forming nanofibers B-nanoparticle or lozenge - like platelets through the use of methanol / water B-material mixtures . [SEP]

[CLS] in pure methanol , folic B-material acid I-material formed a self - supporting gel comprised of discrete nanofibers B-nanoparticle due to the formation of hoogsteen intermolecular pairing of four folic B-material acid I-material molecules ( fig . 2a ) . [SEP]

[CLS] gradual addition of water B-material to this gel led to the emergence of the lozenge - like platelets , which comprise closely packed short nanorods B-nanoparticle of tetramers . [SEP]

[CLS] it was postulated that the increasing water B-material content disrupted the long fibrous structures present to give the more compact platelet structures . [SEP]

[CLS] interestingly , similar treatment of the anticancer B-property drug methotrexate B-material did not induce formation of any well - defined nanostructures , likely due to the lack of hydrogen B-material bond acceptors in methotrexate B-material preventing formation of the tetrameric discs that are the basis of the higher order structures . [SEP]

[CLS] dissolution of hydrophobic B-property drugs in an organic solvent followed by dilution into water B-material is a technique that can provide insight into a drug ' s self - aggregation behavior . [SEP]

[CLS] for example , the quinoline alkaloid camptothecin ( cpt ) , a topoisomerase i inhibitor , has been observed to self - associate through offset faceto - face - interactions ( j - type aggregation ) . [SEP]

[CLS] more recently , hao and coworkers characterized 100 - 400 nm wide helical nanoribbon structures formed from the injection of a concentrated dmso solution of cpt into water B-material ( fig . 2b ) . [SEP]

[CLS] these nanostructures were composed of the active lactone form of cpt and exhibited reversible disassembly - assembly behavior in response to ph modulation . [SEP]

[CLS] increasing the ph led to the formation of the soluble B-property , but inactive , carboxylate B-material form of cpt ; adding acid then reversed the equilibrium to reform the helical nanoribbons . [SEP]

[CLS] fourier - transform infra - red ( ft - ir ) spectroscopy B-technique indicated the presence of hydrogen B-material bonding interactions , and x - ray diffraction experiments suggested that a lamellar structure existed within the nanoribbons . [SEP]

[CLS] the authors thus proposed a packing model in which cpt molecules stack through - interactions and interact with neighboring ' stacks ' via hydrogen B-material bonding . [SEP]

[CLS] another interesting example was recently reported by yan and colleagues in which two drugs , the water soluble cpt derivative irinotecan ( ir ) and the water B-property insoluble ( hydrophobic B-property ) chlorambucil ( cb ) , were directly conjugated to one another to give an amphiphilic B-property drug - drug conjugate ( addc ) ( fig . 2c ) . [SEP]

[CLS] by diluting a dmso solution of the addc with water B-material , uniform nanoparticles B-nanoparticle with hydrodynamic diameters averaging 88 nm were obtained ( fig . 2d ) . [SEP]

[CLS] interestingly , concentrations below the critical aggregation concentration ( cac ) were found to be inactive , whereas above the cac they quickly became toxic B-property , with some indication of synergistic action . [SEP]

[CLS] it was thus proposed that only the nanoparticle B-nanoparticle form of the conjugate , rather than the free monomers B-material , can be internalized by cells B-material . [SEP]

[CLS] this approach was also recently extended to create another addc from the anticancer B-property drugs floxuridine ( fdu ) and bendamustine ( bdm ) . [SEP]

[CLS] in general , the self - assembly of free drug molecules is a somewhat haphazard process , with little control over the resultant morphology . [SEP]

[CLS] exploiting such behavior is therefore difficult at best and its study is accordingly rooted in understanding how the pharmacokinetic properties and treatment efficacy is affected . [SEP]

[CLS] should a discrete nanostructure even be formed , there is no guarantee that it would possess desirable physicochemical properties suitable for clinical treatments . [SEP]

[CLS] to gain access to , and control over , more complex nanostructures it is therefore necessary to introduce modifications to the drug , in particular the design and synthesis of drug - conjugates where other elements are chemically grafted to the drug in order to imbue a greater propensity for controlled self - assembly and the formation of well - defined , homogeneous nanostructures . [SEP]

[CLS] this approach aims to take advantage of the potential interactions that the drug has to offer , thus making the drug a vital structural element rather than just a functional unit . [SEP]

[CLS] the following sections will focus on a number of recent strategies that are being used to further improve the delivery of drugs via construction of nanostructures , creating entities that have been termed onecomponent nanomedicines . [SEP]

[CLS] the advent of nanotechnological approaches to drug delivery began with the development of polymerdrug conjugates in which hydrophobic B-property anticancer B-property drugs were covalently attached to water B-property - I-property soluble B-property polymers B-material , such as n - ( 2 - hydroxypropyl ) methacrylamide ( hpma ) and polyglutamic acid ( pga ) . [SEP]

[CLS] in this strategy , the pharmacokinetic profile of the resultant conjugate ( tissue accumulation , circulation half - life ) is determined by the nature of the polymer B-material , and controlled release can be achieved by choosing appropriate polymer - drug linkages B-property . [SEP]

[CLS] in theory , this combination of properties should lead to increased treatment efficacy and reduced side - effects , but issues with polydispersity in both the degree of polymerization and extent of drug attachment may cause significant batch - to - batch variability that could complicate the efficacy studies and thus hinder further optimization of the system . [SEP]

[CLS] accordingly , these have contributed to the protracted translation of polymer B-material - drug conjugates into clinical use . [SEP]

[CLS] in 1990 , yokoyama and kataoka reported on the synthesis of a doxorubicin B-material ( dox ) - conjugated block copolymer that can assemble into micelles B-material , one of the earliest examples of a rationally designed macromolecular amphiphilic B-property prodrug ( map ) . [SEP]

[CLS] in this map , a poly ( ethylene ) glycol ( peg ) was linked to poly ( aspartic acid ) ( p ( asp ) ) to create the block copolymer , followed by the conjugation of dox to the carboxylic B-material acid I-material function of the p ( asp ) segment ( fig . 3a ) . [SEP]

[CLS] in this particular system , the combination of the hydrophilic B-property peg block with hydrophobic B-property dox results in the formation of micelles B-material with diameters averaging 50 nm . [SEP]

[CLS] these micelles B-material were formed during the extensive aqueous dialysis of the n , ndimethylformamide ( dmf ) reaction solution that followed dox conjugation . [SEP]

[CLS] removal of dox that was physically entrapped within the micelles B-material initially proved difficult , though later optimization of the preparation was able to address this . [SEP]

[CLS] one issue that is commonly found for such systems is the difficulty to achieve complete conjugation of the drug to all available reactive sites due to steric hindrance . [SEP]

[CLS] in one example of kataoka ' s polymer B-material - drug conjugate , there are approximately 17 aspartic B-material acid I-material residues available as conjugation sites yet only a maximum of 53 % coverage with dox could be obtained , though it should also be noted that this gives a respectable drug content of 39 % ( w / w ) . [SEP]

[CLS] the unreacted , ionizable B-property sites could potentially reduce the conjugate ' s capacity for self - assembly at lower concentrations . [SEP]

[CLS] it was determined that a drug coverage of 40 - 50 % was necessary in order to overcome the electrostatic repulsions for formation of stable micelles B-material . [SEP]

[CLS] given the polydispersity native to such systems , some conjugates may not assemble at pharmaceutically relevant concentrations and potentially have very different physicochemical properties and circulation fates . [SEP]

[CLS] indeed , biodistribution studies showed that conjugates which could not maintain a micellar structure underwent rapid renal excretion , whereas the micellar form exhibited prolonged circulation times . [SEP]

[CLS] a later formulation of this map , known as nk911 , underwent phase i clinical trials , exhibiting a higher and more prolonged plasma concentration than free dox , though little difference in toxicity B-property compared to free dox was seen . [SEP]

[CLS] comparisons with historical data from trials involving a liposomal B-nanoparticle dox formulation ( doxil® ) showed that nk911 was cleared more rapidly at the same dosage , an observation attributed to its lower plasma stability . [SEP]

[CLS] however , despite the lower plasma concentration , nk911 was able to more widely distribute dox within tumorous B-material tissues than doxil , potentially due to greater leakage of nk911 from tumor B-material vessels and its subsequent diffusion to distant cancer cells B-material . [SEP]

[CLS] a number of similar maps to that developed by yokohama and kataoka have been reported in later studies . [SEP]

[CLS] in particular , matsumura and coworkers adapted this approach to incorporate sn - 38 , the active metabolite of irinotecan , though p ( asp ) was replaced with poly - glutamate , p ( glu ) . [SEP]

[CLS] this map exhibited significant advantages over free irinotecan in animal models with respect to both efficacy and toxicity B-property . [SEP]

[CLS] phase i clinical trials generally showed milder side - effects in comparison to the free drug , and though phase ii trials are listed [SEP]

[CLS] as having been completed within the last few years ( id # nct00951613 and nct00951054 ) , no data has yet been made available . [SEP]

[CLS] more recently , zhang and colleagues utilized this strategy to construct similar supramolecular nanostructures of the anticancer B-property drugs doxorubicin B-material and camptothecin , employing reversible addition - fragmentation chain B-property transfer I-property ( raft ) polymerization to provide greater control over the polydispersity . [SEP]

[CLS] an interesting approach for the delivery of cisplatin B-material ( cis - diaminodichloroplatinum ( ii ) , cddp ) was also developed by yokoyama and kataoka , relying on the formation of coordination bonds between the pt atom B-material and the p ( glu ) carboxylate B-material side - chains ( fig . 3b ) . [SEP]

[CLS] when mixed in water B-material , cddp cross - links the peg - p ( glu ) polymer B-material chains , resulting in the spontaneous formation of micelles B-material that were approximately 28 nm in diameter . [SEP]

[CLS] when compared with those of the 50 nm micellar dox - conjugates , it can be seen how the drug type can influence the nanostructure ' s properties . [SEP]

[CLS] it was proposed , in this instance , that the ability of the pt atom B-material of cddp to form two bonds to the polymer B-material in addition to its smaller size allows the formation of a smaller , denser micelle B-material . [SEP]

[CLS] release of cddp was predicated on ligand exchange between the carboxylates B-material and free chloride B-material ions B-material . [SEP]

[CLS] compared with an earlier version of this map based on peg - p ( asp ) , the release profiles indicated greater micellar stability , with pt released in a sustained manner over 150 hr ( no burst release ) and the nanostructures maintaining diameters over 25 nm for at least 50 hr . [SEP]

[CLS] consequently , this stability led to excellent in vivo efficacy , with further studies showing a reduction in both nephro - and neurotoxicity and the potential for targeted delivery to lymph node metastases B-event . [SEP]

[CLS] this promising platform , also known as nc - 6004 , is currently undergoing a number of clinical trials , both as a single treatment and in combination with the antimetabolite gemcitabine , against a number of cancer types , including a phase iii trial against pancreatic cancer ( id # nct02043288 ) . [SEP]

[CLS] the polymer - drug conjugates developed by yokayama and kataoka represent a very simple embodiment of the principles behind macromolecular amphiphilic B-property prodrugs , relying on the enhanced permeation and retention ( epr ) effect to passively target tumors B-material . [SEP]

[CLS] to imbue greater functionality to the assembled system , such as the capacity for active targeting of tumors B-material , it is therefore necessary to explore other chemical entities and introduce greater complexity . [SEP]

[CLS] one such example is provided by liu and coworkers , who developed an amphiphilic B-property polymer B-material - drug conjugate based on cpt that possessed folic B-material acid I-material receptor targeting ligands , photo - triggered drug release and cross - linkers sensitive to both acidic and reductive environments ( fig . 4a ) . [SEP]

[CLS] this strategy was based on co - assembly of two diblock copolymers , one that contained a folic B-material acid I-material ( fa ) ligand and one that contained a block of photo - caged cpt molecules . [SEP]

[CLS] cosolvation of these two entities in dmso followed by the addition of aqueous buffer led to formation of micelles B-material , which were then stabilized by crosslinking . [SEP]

[CLS] these fa - decorated shell cross - linked micelles B-material possessed a hydrodynamic diameter of ~ 54 nm , could be effectively internalized into a549 human lung adenocarcinoma epithelial cells B-material , and demonstrated excellent in vitro cytotoxicity B-property . [SEP]

[CLS] while liu ' s system is an impressive feat of design and synthesis , it also serves to illustrate that greater complexity can come at a cost , with an increased number of potential issues associated with the varying degrees of polydispersity ( polymer B-material molecular weight , number of conjugated drugs , crosslinking coverage ) among the micelles B-material that could complicate future translational studies . [SEP]

[CLS] despite such concerns , a tradeoff between greater functionality and increased complexity must be made to achieve the desired aims of a drug delivery platform . [SEP]

[CLS] the macromolecular components that constitute maps are not solely limited to conventional hydrophilic B-property polymers B-material . [SEP]

[CLS] for instance , an interesting series of conjugates developed by chilkoti and colleagues exploits the thermally responsive properties of elastin - like peptides B-material ( elps ) . [SEP]

[CLS] at low temperatures elps exist in a random conformation that renders them soluble B-property , but at higher temperatures a conformational change occurs that lowers the solubility B-property and can induce aggregation . [SEP]

[CLS] in 2009 , chilkoti and coworkers reported an elp - based drug - polypeptide B-material conjugate that could self - assemble into spherical nanostructures ; a platform that was developed from previous work that utilized genetically engineered elps to thermally target solid tumors B-material whose temperature had been raised by selective heat treatment . [SEP]

[CLS] the peptidic segment comprised the sequence skgpg ( xgvpg ) 160wpc ( g2c ) 7 , with the cysteine B-material residues included for the conjugation of up to eight drug molecules ( fig . 4b ) . [SEP]

[CLS] a number of drug and drug - like molecules were tested , indicating that the octanol - water B-material distribution coefficient , log d , is the critical determinant in the conjugate ' s ability to self - assemble . [SEP]

[CLS] the more hydrophobic B-property the drug is , the better able it is to help induce nanostructure formation [SEP]

[CLS] in this example , the conjugation of dox created a hydrophobic B-property region that confers amphiphilicity B-property to the conjugate . [SEP]

[CLS] upon dispersal in water B-material , these conjugates self - assembled into nanoparticles B-nanoparticle with narrowly distributed hydrodynamic diameters of 21 nm and a cac value of 3 m ( fig . 4c ) . [SEP]

[CLS] in vivo experiments indicated that the nanoparticles B-nanoparticle experienced prolonged circulation , increased tumor B-material accumulation and reduced uptake in non - tumor B-material targets . [SEP]

[CLS] remarkably , a single - injection dose appeared to cure eight of nine mice for up to 66 days posttumor implantation , compared with median survival times of 21 and 27 days for the saline and free dox control groups , respectively . [SEP]

[CLS] subsequent studies have further highlighted the promise this system possesses as a viable treatment option , especially with regards to the thermal targeting of tumors B-material . [SEP]

[CLS] heating of the tumor B-material induces a phase transition in the conjugate , triggering aggregation that traps the nanoparticles B-nanoparticle within the tumor B-material vasculature . [SEP]

[CLS] upon cooling , a steep transvascular concentration gradient with the external soluble B-property nanoparticles B-nanoparticle is created that facilitates further transport into the tumor B-material environment ( fig . 4d - e ) . [SEP]

[CLS] this behavior illustrates how further functionality can be effectively imparted through rational design choices , in particular the consolidation of multiple functions ( hydrophilicity B-property and targeting ) into a single segment . [SEP]

[CLS] the nanostructure morphology formed through self - assembly of maps is another important feature that can have a significant effect on how it will perform . [SEP]

[CLS] since the self - assembly of block copolymers is typically under kinetic and thermodynamic control , it can be influenced by the various factors at play : cosolvent composition , polymer B-material concentration , temperature and the rate of water B-material addition . [SEP]

[CLS] liu and coworkers exploited this behavior to induce a peg - polycpt diblock copolymer , synthesized via raft polymerization , to form nanospheres B-nanoparticle , nanodisks , staggered lamellae structures and large compound vesicles . [SEP]

[CLS] liu found that the adopted structure could significantly affect the cellular internalization , not only in terms of the uptake efficiency , but also with regard to the mechanism of membrane transport . [SEP]

[CLS] the most effective uptake was seen for the staggered lamellae structures , which effectively bypassed the endolysosomal compartments and dispersed well throughout cells B-material . [SEP]

[CLS] this greater uptake also resulted in this morphology exhibiting the greatest in vitro cytotoxicity B-property . [SEP]

[CLS] whether this will translate into a greater in vivo efficacy will be interesting to learn , but for now liu ' s polymer B-material - drug conjugate provides a fascinating example of how processing conditions can be utilized to control the morphology , and how different structures could affect their cellular interactions and overall efficacy [SEP]

[CLS] macromolecular amphiphilic B-property prodrugs have demonstrated great potential for delivering a drug payload through the drug - induced formation of nanostructures . [SEP]

[CLS] their development has benefitted greatly from the years of research that has been performed on polymeric delivery systems in general , with protocols for determining their properties already well established , and it is no surprise that a number are already in advanced clinical trials . [SEP]

[CLS] for the most part , maps are synthetically facile to create , though can suffer from polydispersity issues . [SEP]

[CLS] advances in polymer B-material synthesis techniques have alleviated this to some degree , providing greater control over the polymer B-material size and enabling a more homogeneous polymer - drug conjugate to be produced , but the issue has not been completely eliminated and may still complicate translational studies . [SEP]

[CLS] stability during circulation is one concern that has already arisen , for instance , and others may arise from the reliance on the epr effect as the dominant method of targeting . [SEP]

[CLS] further research into more active targeting strategies is desirable , though this could come at the cost of potentially increased synthetic complexity . [SEP]

[CLS] amphiphilic B-property prodrugs ( aps ) represent the next logical step in the evolution of self - delivering drugs ; rather than conjugating the drug to a polymeric entity as in macromolecular amphiphilic B-property prodrugs , a discrete entity that imbues the desired characteristics is utilized . [SEP]

[CLS] this approach offers several advantages , one being that precise control over the drug content can be more easily achieved through rational molecular design . [SEP]

[CLS] furthermore , homogeneity is practically assured as the synthesized conjugate can be purified using hplc and the nanostructure formed will contain the same drug content . [SEP]

[CLS] there are no issues such as polydispersity in the macromolecular component or extent of drug conjugation per unimer . [SEP]

[CLS] given the lower molecular weight of aps , the drug becomes an integral part of the structure and as such can exert a great influence over the self - assembly pathway . [SEP]

[CLS] an early strategy in the development of aps was the lipidation B-event of hydrophilic B-property nucleoside - based drugs , an approach pioneered by both jin and couvreur . [SEP]

[CLS] in all reports , nanoparticles B-nanoparticle were obtained using the precipitation method in which an organic solvent solution of the amphiphilic B-property prodrug was added to aqueous buffer . [SEP]

[CLS] these methodologies were applied to a number of different drug types , including antivirals B-property , antineoplastics , antibiotics and even anti - parasitics . [SEP]

[CLS] later research efforts conjugated a hydrophilic B-property element to hydrophobic B-property drugs , again relying on the precipitation method to generate nanoscale objects . [SEP]

[CLS] shen and coworkers , for example , created vesicle - like nanocapsules B-nanoparticle from oligoethylene glycol ( oeg ) - conjugated camptothecin . [SEP]

[CLS] these nanocapsules B-nanoparticle could also load a second anticancer B-property drug , doxorubicin B-material , for delivery in a fashion similar to that of the clinicallyrelevant liposomal B-nanoparticle formulation , doxil . [SEP]

[CLS] it is evident , however , that the nanoprecipitation approach has limitations in effectively controlling the size , shape and surface chemistry of the resulting nanostructures due to the reliance of kinetic trapping in their assembly . [SEP]

[CLS] by solely utilizing hydrophobic B-property collapse as the primary driving force for forming nanostructures , there is less opportunity to direct how the rationally designed molecules arrange themselves within the resultant nanostructure . [SEP]

[CLS] consequently , the majority of ongoing research in amphiphilic B-property prodrug design has focused on the introduction of additional elements that can contribute reversible and directional interactions to allow for a better controlled self - assembly pathway . [SEP]

[CLS] an early example of an amphiphilic B-property prodrug that exhibited self - assembly behavior was reported by cui and coworkers , who created a " drug amphiphile B-property " platform in which a hydrophobic B-property drug is conjugated to a short peptide B-material with overall hydrophilicity B-property and a preference for - sheet formation . [SEP]

[CLS] the generic design of these drug amphiphiles B-property is illustrated in fig . 5a , and comprises the hydrophobic B-property drug , a degradable linker for stimuli - triggered release , and a peptide B-material segment that contains a structure - directing motif ( e . g . sheet , - helix ) and charged amino B-material acids I-material ( or biologically relevant peptides B-material ) . [SEP]

[CLS] the peptide B-material segment is a critical inclusion as the many natural and synthetic amino B-material acids I-material available allows for customization of the platform with regard to morphology , physicochemical properties and targeting ability . [SEP]

[CLS] cui ' s demonstration of this strategy conjugated the hydrophobic B-property cpt to the - sheet forming tau peptide B-material ( vqivyk ) via reducible disulfide B-property linkages I-property ( fig 5b ) . [SEP]

[CLS] the drug content was precisely controlled through the introduction of branching points so that one , two or four cpt molecules were attached to give drug loadings of 23 , 31 and 38 % , respectively . [SEP]

[CLS] when dissolved in water B-material , these conjugates assembled into one - dimensional ( 1d ) filamentous structures in which the hydrophobic B-property drug was sequestered within the core B-material and thus protected from the external environment ( fig . 5c - e ) . [SEP]

[CLS] dilution studies of the assembled drug amphiphiles B-property revealed they were stable at nano - molar concentrations , indicative of the strong associative interactions within the nanostructures . [SEP]

[CLS] interestingly , while the drug amphiphiles B-property containing one and two cpt molecules gave nanofilaments ( fig . 5c and d ) , qcpt - buss - tau ( four conjugated cpt molecules ) was observed to adopt a nanotube B-nanoparticle morphology ( fig . 5e ) . [SEP]

[CLS] the narrow diameter of these tubes ( approx . 9 . 5 ± 1 nm ) indicates that they are formed from a monolayer of amphiphiles B-property , such that the internal channel is lined by hydrophobic B-property cpt molecules . [SEP]

[CLS] the origin of this change in morphology that the higher drug content induced was found to be due to the effect of - interactions between the cpt molecules , presumably both intra - and intermolecular associations . [SEP]

[CLS] replacement of the tau peptide B-material with the more hydrophilic B-property - sheet - forming sup35 peptide B-material ( n2q2ny ) , gave the same nanotube B-nanoparticle structure with the only difference being a longer contour length that may be a consequence of the greater solubility B-property this peptide B-material confers , suggesting that it is the arrangement of cpt molecules that is the major driving force behind this morphology . [SEP]

[CLS] the protection that the nanostructures provide the cleavable linker was illustrated by subjecting the conjugates to degradation by hydrolysis and reduction . [SEP]

[CLS] in all cases , glutathione - induced release was faster than hydrolysis alone as would be expected . [SEP]

[CLS] it was seen that the more hydrophobic B-property conjugates ( dcpt - buss - tau and qcpt - buss - tau ) provided the greatest protective effect , consistent with their more stable structures . [SEP]

[CLS] a degradation study of mcpt - buss - tau at two different concentrations showed that the release was faster at low concentrations where the equilibrium between monomer B-material and nanostructure would be in favor of a higher ratio of monomers B-material to nanostructures . [SEP]

[CLS] this clearly indicates how the drug amphiphiles B-property can act as a reservoir for the bioactive drug , with the nanostructure undergoing dissociation to monomers B-material at the target site that can then degrade to release free drug ( fig . 5f ) . [SEP]

[CLS] however , an unintended consequence of the protection provided later became apparent , as a more mechanistic study into the release showed that the cytotoxicity B-property of the mcpt - buss - tau conjugate was being compromised by the formation of hydrophobic B-property cpt - containing disulfide species . [SEP]

[CLS] upon reduction , the close proximity of molecules within the assembly promoted the formation of the symmetrical disulfide species , which would then remain closely associated with the nanostructure or form their own aggregates . [SEP]

[CLS] switching to an ethyl carbonate B-material disulfide linker that can undergo rapid intramolecular degradation upon cleavage was found to restore the toxicity B-property to almost that of the free cpt . [SEP]

[CLS] these observations emphasize the importance of considering how the nanostructure will affect the desired release mechanism of the free drug . [SEP]

[CLS] it is often assumed that the release mechanism will function as designed , but in a self - assembled system access to the linker may be limited by the density of packing , and with such high local monomer B-material concentrations side reactions are also a possibility . [SEP]

[CLS] replacement of the cpt in the drug amphiphile B-property with the bulky taxane paclitaxel B-material ( ptx ) was found to also give filamentous nanostructures with a fixed 41 % drug loading . [SEP]

[CLS] however , while the morphology was unaltered there was a clear difference in the physical properties of the nanostructures , with the cac value determined to be 10 m , an almost 50 - fold increase on that of the analogous cpt conjugate . [SEP]

[CLS] it is evident that the bulkier ptx molecule affects the internal packing order within the nanostructure and a higher concentration must therefore be achieved before the energetics become favorable enough to induce self - assembly . [SEP]

[CLS] furthermore , a drug amphiphile B-property that contained two ptx molecules was only able to form spherical and very short filament - like structures upon dissolution in water B-material . [SEP]

[CLS] no evidence of a - sheet could be found , indicating that the two bulky ptx molecules prevented the peptide B-material segment from forming the requisite hydrogen B-material bonds that would promote elongation . [SEP]

[CLS] these studies underscore how the design of drug amphiphiles B-property must take into account the affect the drug will have on assembly . [SEP]

[CLS] while it may be possible to switch out drugs of similar structure without creating problems , it must be assessed how drugs with dramatically different molecular structures will influence the assembly . [SEP]

[CLS] it is evident that the packing arrangement of molecules plays a critical role during the self - assembly process ; behavior that can be exploited in order to produce new and interesting architectures . [SEP]

[CLS] in one report , cui and coworkers combined both cpt ( flat aromatic with a preference for - interactions ) and ptx ( bulky with the potential for hydrogen B-material bonding ) into a single drug amphiphile B-property . [SEP]

[CLS] borne out of the molecular frustration induced by having such disparate structural entities in close proximity , the conjugate initially forms small , flexible filamentous structures 7 - 8 nm in width ( fig . 6a ) , eventually evolving into long twisted two - filament fibrils ~ 14 nm in width ( fig . 6b ) . [SEP]

[CLS] it was postulated that the initial short filaments were the kinetic product of the hydrophobic B-property collapse , with further rearrangement of the internal structure allowing the formation of - sheet hydrogen B-material bonds to give twisted two - filament fibrils as the thermodynamic product . [SEP]

[CLS] a second approach was demonstrated by the catanionic mixing of oppositely charged derivatives of cui ' s four - cpt bearing drug amphiphile B-property , qcpt - sup35 - k2 and qcpt - sup35 - e2 , which led to the formation of large , multi - walled nanotubes B-nanoparticle ( fig . 6c ) ; very distinct structures from the smaller nanotubes B-nanoparticle formed by the individual components . [SEP]

[CLS] it was proposed that ion B-material pair formation between the two oppositely charged drug amphiphiles B-property leads to a reduction in the headgroup volume , thereby facilitating the formation of the bilayer ( s ) that constitutes the nanotube B-nanoparticle walls . [SEP]

[CLS] the drug amphiphile B-property that cui is developing is designed to be a modular platform that can be adapted towards a particular mode of delivery . [SEP]

[CLS] as it currently stands , the exclusive formation of filamentous structures is more suited toward local delivery applications given the potential that such structures have for entanglement and hydrogel formation . [SEP]

[CLS] however , there are reports of long nanofilaments being used for systemic delivery of cytotoxic B-property agents , so with suitable modification of the surface chemistry applications requiring systemic delivery cannot be ruled out . [SEP]

[CLS] further fine tuning of the peptide B-material sequence can also impart the ability to adopt different structures depending on the solution conditions . [SEP]

[CLS] for example , goldberger and coworkers demonstrated that a peptide B-material amphiphile B-property could form either nanofibrous or spherical micellar structures depending on the solution ph and amphiphile B-property concentration . [SEP]

[CLS] a number of other research groups have also investigated the use of drug - peptide B-material amphiphiles B-property that can self - assemble into well - defined nanostructures . [SEP]

[CLS] a collaboration between the labs of grinstaff and parquette , for instance , led to the creation of a simple conjugate in which cpt was attached to the amine B-material of the c - terminal lysine B-material in a lys - lys dipeptide ( 47 % drug loading ) ( fig . 7a ) . [SEP]

[CLS] dissolution of the solid form in pbs and subsequent aging led to the formation of large nanotubule structures with diameters ranging from 80 to 120 nm and lengths of several micrometers . [SEP]

[CLS] while they were found to have a very high cac value ( 350 m ) , once formed they were exceptionally stable and would only dissociate in the low nm concentration range . [SEP]

[CLS] in vitro assays confirmed that the nanotubes B-nanoparticle possessed good activity against a range of human colorectal and non - small cell B-material lung cancer cell B-material lines . [SEP]

[CLS] their large size and lack of flexibility , however , may prove to be detrimental for both systemic and local delivery applications . [SEP]

[CLS] dong and colleagues reported on the conjugation of hydroxyl - camptothecin ( hcpt ) to a multidomain peptide B-material , the self - assembly of which results in short nanofilament structures that were 6 - 7 nm wide and no more than 50 nm long . [SEP]

[CLS] the shorter nature of these nanostructures may hold advantages over longer nanofilaments for more effective cellular uptake . [SEP]

[CLS] ding and coworkers reported another example in which the conjugation of ptx to a tumor - homing cell - penetrating peptide B-material ( cpp ) resulted in the formation of spherical nanostructures ~ 120 nm in diameter . [SEP]

[CLS] an intriguing strategy has been developed by zhang and coworkers , who exploited the properties of spherical nucleic B-material acids I-material ( snas ) to create dna - drug amphiphiles B-property . [SEP]

[CLS] snas , which are normally based on a dna shell B-material around a solid core B-material such as a gold B-nanoparticle nanoparticle I-nanoparticle , have been shown to have exceptional cellular uptake properties and stability towards enzymatic degradation . [SEP]

[CLS] zhang ' s approach was to replace the gold B-nanoparticle nanoparticle I-nanoparticle core B-material with a drug reservoir . [SEP]

[CLS] in this work , three molecules of cpt were conjugated to a strand of dna via a photo - sensitive linkage B-property ( fig . 7b ) , such that uv irradiation will trigger the irreversible release of free drug . [SEP]

[CLS] the aqueous self - assembly behavior was found to be dependent upon the length of the dna strand , with five base pairs giving a spherical micellar structure 28 ± 5 nm ( determined by tem ) ( fig . 7c ) . [SEP]

[CLS] increasing the length of the strand eventually resulted in assembly being disfavored once the number of bases exceeded nine , which the authors attribute to reduced aggregation numbers as a consequence of the increasing volume within the head of the amphiphile B-property . [SEP]

[CLS] in the presence of mg 2 + ions B-material , however , self - assembly could be observed in all the dna - drug amphiphiles B-property synthesized ( up to 20 bases ) . [SEP]

[CLS] this was attributed to the ability of the divalent cation B-material to bridge neighboring strands and overcome the entropic penalty incurred during the assembly of densely packed nanostructures . [SEP]

[CLS] surprisingly , the largest dna - drug amphiphile B-property , dna20 - cpt , adopted a rod - like morphology with diameters of 8 ± 1 nm and lengths 53 ± 14 nm ( fig . 7d ) , an observation that is still under investigation . [SEP]

[CLS] in vitro studies of the dna20 - cpt showed that they retained their capacity for highly efficient cellular uptake , exhibiting comparable activity to free cpt against sk - br3 ovarian cancer cells B-material under uv irradiation . [SEP]

[CLS] zhang ' s focus on the activity of the longer dna - drug conjugate lies in the utility of dna sequences with lengths of 18 - 25 bases for gene regulation applications , suggesting potential use of the dna - drug amphiphiles B-property for combination therapy - simultaneous chemo - and genetherapies in this instance . [SEP]

[CLS] overall , dna - drug amphiphiles B-property possess great potential as drug delivery vehicles B-material , though a major hurdle is the promiscuity that snas display towards cellular internalization . [SEP]

[CLS] more selective delivery has been demonstrated using conjugated antibodies B-material , an encouraging result for the development of a viable delivery platform . [SEP]

[CLS] amphiphilic B-property prodrugs represent an intriguing new class of drug delivery vehicles B-material , one that holds the promise of customization to suit a particular therapeutic application . [SEP]

[CLS] the modular design that many of the platforms in development exhibit imbues them with the capacity for fine tuning of the nanostructure morphology and physicochemical properties , making them adaptable for local and systemic delivery . [SEP]

[CLS] given that aps are still at an early stage of development , there are a number of concerns that have been raised , particularly with regard to the stability of the resulting nanostructures . [SEP]

[CLS] while the cac of the assembly is typically seen as the defining property , it is perhaps the resistance to disassembly upon dilution that is of greater import . [SEP]

[CLS] asymmetry in these two phenomena is quite possible for instance , as though a relatively high concentration may be required for assembly to occur , the strong intermolecular B-property interactions I-property that may form during this process could result in a much lower disassembly concentration . [SEP]

[CLS] how this will play into in vivo efficacy remains to be determined , however , and may be challenging to ascertain . [SEP]

[CLS] concurrent advances in nanotechnological approaches to in vivo imaging may provide some assistance with this , as similar concerns will exist over the circulation fate of nanoprobes B-nanoparticle that possess similar physicochemical properties to nanostructures formed by aps . [SEP]

[CLS] one other aspect that needs to be addressed is the adaptability of the platform with respect to the incorporated drug . [SEP]

[CLS] the smaller nature of aps means that the drug can play a much larger role in the selfassembly process when compared with maps , and while the polymeric nature of the latter may compensate for any reluctance toward assembly from the drug , this will not be the case in the former . [SEP]

[CLS] thus far , the majority of the work reported has focused on the use of the hydrophobic B-property cpt as a model drug owing to its planar nature , its preference for - interactions , and the ease with which it can modified . [SEP]

[CLS] this does , however , limit our knowledge of how the drug can influence the overall nanostructure and its physicochemical properties . [SEP]

[CLS] cui ' s work has shown that an increased drug loading can affect the self - assembled morphology as the drug ' s own interactions become more dominant , [SEP]

[CLS] and that steric effects too can cause variations in the self - assembly pathway . [SEP]

[CLS] more investigation is therefore required , as it will only be once a wider range of drug structure classes have been explored that we will learn if amphiphilic B-property prodrug platforms have the expected broad utility , or if they will be limited to certain drug types . [SEP]

[CLS] molecular hydrogelators are a special class of amphiphilic B-property molecules that are designed to spontaneously form a self - supporting gel when dispersed in water B-material . [SEP]

[CLS] this typically occurs through self - assembly into filamentous nanostructures that then entangle to create a three - dimensional network that traps the water B-material and prevents its free movement . [SEP]

[CLS] compared with their polymer - based counterparts , molecular hydrogelators offer several advantages , such as an inherent biodegradability B-property , reversible formationdissociation , and lower immunogenicity B-property . [SEP]

[CLS] in a little over two decades , development of these materials has led to numerous medically - relevant applications , including tissue engineering scaffolds , matrices for biomineralization and wound healing , and as local drug delivery vehicles B-material . [SEP]

[CLS] it is their ability to entrap and release biomolecules and small molecules , in combination with their three - dimensional network structure , which allows their use for biomedical applications . [SEP]

[CLS] the utility of this approach towards drug delivery , however , is limited owing to the physical method of entrapment that , like polymeric delivery vehicles B-material , can suffer from low loading and poor control over the release characteristics . [SEP]

[CLS] additionally , the hydrophilic B-property environment of the gel can result in the crystallization of drugs with low water B-material solubility B-property , which can have a detrimental effect on the therapeutic effectiveness . [SEP]

[CLS] for instance , the hydrophobic B-property ptx has been observed to form crystals within hydrogels , much like those formed in aqueous solution , and it was speculated that this may be the reason why in some studies hydrogels with a lower drug content exhibited greater activity than those with a higher loading . [SEP]

[CLS] modifying drug molecules themselves to bestow the capacity for hydrogelation provides a means for circumventing both the drug crystallization and low loading issues associated with excipient B-property hydrogels . [SEP]

[CLS] drug - based molecular hydrogelators have been in development for almost twenty years now and , in contrast to non - gelating amphiphilic B-property prodrugs , have encompassed a broad range of drug molecules , including inhibitory hormones , antibiotics , anti - neoplastics , antiinflammatories , and anti - virals [SEP]

[CLS] the majority of these hydrogelators are peptide B-material - based , as their propensity for hydrogen B-material bonding is ideal for the formation of the filamentous structures generally required for gelation to occur . [SEP]

[CLS] indeed , a number of peptide B-material drugs are known to form hydrogels themselves ( autogels ) in aqueous conditions , such as lanreotide ( fig . 8a ) , ganirelix ( fig . 8a ) , and degarelix , with lanreotide being approved by the fda for the treatment of acromelagy and neuroendocrine tumors B-material as an injectable sustained release hydrogel ( somatuline® depot , ipsen ) . [SEP]

[CLS] a common feature between these three examples is a naphthalene moiety that , for lanreotide at least , has been shown to significantly contribute to the self - assembly through - interactions . [SEP]

[CLS] xu and coworkers demonstrated that the attachment of a pyrene group to the glycopeptide antibiotic vancomycin confers an ability to form hydrogels ( fig . 8b ) . [SEP]

[CLS] surprisingly , this modified - vancomycin was found to have nearly thousand - fold better activity against vancomycin - resistant enterococci bacteria than vancomycin alone ; an observation later postulated as arising from self - assembly of the conjugate on the bacterial cell B-material surface . [SEP]

[CLS] the modification of non - peptidic drugs to bestow gelation potential typically involves the conjugation of a short peptide B-material sequence capable of forming strong , directional intermolecular B-property interactions I-property . [SEP]

[CLS] a common motif is the dipeptide phe - phe , often in combination with a planar aromatic group at the n - terminal for additional hydrophobicity B-property . [SEP]

[CLS] this dipeptide is the key recognition motif of a amyloid and has been observed to form one dimensional nanostructures through the combination of hydrogen B-material bonding and - interactions . [SEP]

[CLS] xu and colleagues utilized this motif to create the ptxcontaining hydrogelator napffk ( succ - ptx ) py ( fig . 8c ) , conjugating the succinylated - drug to the peptide B-material through the - amine B-material of lysine B-material . [SEP]

[CLS] additionally , the capacity for triggered gelation was introduced through incorporation of a phosphorylated tyrosine B-material residue ( py ) that provides hydrophilicity B-property , but can be cleaved by a phosphatase enzyme to reduce the solubility B-property and induce self - assembly . [SEP]

[CLS] spectroscopic studies showed that the resulting filamentous structures possessed anti - parallel - sheets , indicating that the ptx is likely displayed at the surface of the nanostructures . [SEP]

[CLS] while this may suggest it would be readily accessible , entanglement between filaments will be favored in order to reduce hydrophobic - hydrophilic contacts between the water B-material and ptx , helping to promote gel formation . [SEP]

[CLS] this nap - ffy platform or similar have been further exploited by xu and others in the field to create hydrogelators based on a number of drugs , including the anti B-property - I-property inflammatory I-property olsalazine , the antibiotic kanamycin , and the anticancer B-property drugs bortezemib and cisplatin B-material . [SEP]

[CLS] an alternative conjugation approach is to attach the drug to the n - terminal of the peptide B-material , rather than to one of the amino B-material acid I-material side chains . [SEP]

[CLS] this does , however , place certain limitations on the drug structure in order to maintain the self - assembly properties of the conjugate , requiring flat hydrophobic B-property drugs . [SEP]

[CLS] one class of drugs that seem particularly suited for this are non B-property - I-property steroidal I-property anti I-property - I-property inflammatory I-property drugs ( nsaids ) , which tend to be rather simple aromatic molecules . [SEP]

[CLS] xu and colleagues conjugated the nsaids naproxen ( npx ) , flurbiprofen , ibuprofen and salicylic acid ( as an aspirin mimic ) to the n - termini of the ff peptide B-material . [SEP]

[CLS] examination of the mechanical properties revealed that the drug ' s ability to contribute to the - interactions during self - assembly greatly affect the rheological parameters of the resulting hydrogels , with the naphthyl - based naproxen conjugate furnishing the strongest gel and the phenyl - based ibuprofen the weakest . [SEP]

[CLS] yang , too , has reported hydrogelators in which the drug is attached to the n - terminal of the peptide B-material , using the anticancer B-property drugs curcumin and gemcitabine , both of which possess very different molecular structures to the nsaids , affording gels with g ' and g " values two orders of magnitude lower than those of xu ' s naproxen conjugate . [SEP]

[CLS] the differing peptide B-material sequences make a direct comparison difficult , however , though both curcumin and gemcitabine possess smaller aromatic systems than naproxen and so this may a contributing factor . [SEP]

[CLS] platforms for potential combination therapy applications have also emerged with the creation of molecular hydrogelators that contain two complementary drugs . [SEP]

[CLS] for instance , yang and coworkers synthesized a conjugate that possessed dexamethasone and either of ptx or hcpt ( fig . 8d ) . [SEP]

[CLS] dexamethasone is a steroidal drug with anti B-property - I-property inflammatory I-property and immunosuppressant properties that is often used in combination with other anticancer B-property drugs to reduce the associated side - effects . [SEP]

[CLS] while no benefit was seen to its inclusion in terms of in vitro toxicity B-property , it would be anticipated that there may be advantages in vivo with reduced side effects . [SEP]

[CLS] more recently , xu and colleagues conjugated the anti - hiv drug , lamivudine ( 3tc ) , to the lysine - amine B-material of their npx - ffkpy hydrogelators to create a hydrogel that can deliver both an anti B-property - I-property inflammatory I-property and anti - hiv drug . [SEP]

[CLS] the intent here being to create a multifunctional delivery system to address several issues associated with the use of vaginally - applied anti - hiv gels as prophylactics . [SEP]

[CLS] cleavage of the phosphate group by the prostatic acid phosphatase ( pap ) enzyme present in seminal fluid results in the strengthening of the weak gel formed by npx - ffk ( 3tc ) py , thereby minimizing its dilution . [SEP]

[CLS] release of the npx would reduce local inflammation that would otherwise increase the chances of the hiv virus encountering and entering t cells B-material , and the 3tc would act against the virus itself . [SEP]

[CLS] this concept of incorporating two complementary drugs offers an intriguing path for future hydrogel platforms that could provide synergistic effects during treatment . [SEP]

[CLS] despite the proliferation of hydrogels that are based on the diphenylalanine motif , there are a number of other strategies that have generated useful platforms for drug delivery . [SEP]

[CLS] one such simple approach is the succinylation of a hydrophobic B-property drug in order to confer amphiphilicity B-property . [SEP]

[CLS] chen and coworkers treated the corticosteroid trimamcinolone acetonide ( ta ) with succinic anhydride to form a progelator that , upon hydrolysis of the succinate ester bond , would form a hydrogel . [SEP]

[CLS] this gel was used to treat uveitis in a rat model without exhibiting any of the associated complications that usually arise from ta treatment . [SEP]

[CLS] yang and colleagues also found that succinylated ptx can be induced to form a gel through sonication of a suspension . [SEP]

[CLS] the gel formed , however , was very weak and required the addition of a polymer B-material additive ( hyaluronic acid , ha ) to strengthen it . [SEP]

[CLS] surprisingly , this had the added bonus of improving the anti - tumor activity for gels with 30 % or higher ha content , possibly due to the ability of ha to target the cd44 antigen that is often over - expressed in cancer cells B-material . [SEP]

[CLS] in another example of simple conjugation to a drug molecule , yang and coworkers connected the oxidized form of glutathione to ptx via a succinyl linkage B-property that upon reduction could form a hydrogel . [SEP]

[CLS] the mechanical properties of this hydrogel were such that it was suitable for administration as an injectable ; being able to flow as a liquid under shear stress but recovering within a few minutes once the stress was removed ( shear thinning behavior ) . [SEP]

[CLS] intra - tumoral injection of the gel in a mouse model was found to significantly inhibit tumor B-material growth and metastasis B-event , with noticeably lessened or absent side effects . [SEP]

[CLS] stupp and coworkers have demonstrated that their hydrogel - forming peptide B-material amphiphile B-property platform can be adapted to sustainably release a number of drug types . [SEP]

[CLS] stupp ' s peptide B-material amphiphiles B-property are typically - sheet forming peptides B-material with charged amino B-material acids I-material at the c - terminal end and a palmitoylated ( c16 ) n - terminus that self - assemble into core - shell nanofiber B-nanoparticle structures . [SEP]

[CLS] conjugation of the drugs was achieved through the lysine B-material - amine B-material of c16 - vxaxexk ( x = 2 or 3 ) , resulting in nanostructures in which the drug is exposed at the periphery and thus accessible to the agents required for cleavage . [SEP]

[CLS] gelation was achieved by the addition of cacl2 to shield the negative charges of the glutamates and reduce inter - fiber repulsions . [SEP]

[CLS] this method was utilized for the sustained release of the nsaids nabumetone and naproxen , the steroidal B-property anti B-property - I-property inflammatory I-property dexamethasone , and therapeutic carbon B-material monoxide . [SEP]

[CLS] it should also be noted that cui ' s drug amphiphile B-property platform can be similarly adapted for hydrogel - mediated delivery of drugs , with the filamentous nanostructures formed capable of entangling under appropriate conditions in the same manner as stupp ' s peptide B-material amphiphiles B-property . [SEP]

[CLS] an interesting example worth highlighting is that of a hydrogel formed through the gelation of nanospheres B-nanoparticle rather than nanofilaments , a somewhat intriguing exception to the norm . [SEP]

[CLS] created by yang and coworkers , the conjugate fa - gpyk ( succ - ptx ) , where fa is folic B-material acid I-material , was observed to form a clear gel upon phosphatase - catalyzed removal of the tyrosine B-material phosphate group ( fig . 9a ) . [SEP]

[CLS] afm imaging revealed the presence of highly uniform nanospheres B-nanoparticle with diameters of 50 nm ( fig . 9b ) , a structure that may arise from the capability of folic B-material acid I-material to form tetrameric structures through hoogsteen hydrogen B-material bonding , with further interactions giving a dendrimer - like structure ( fig . 9c ) . [SEP]

[CLS] rheological studies indicated that the gel was very weak , no doubt due to the inability of nanoparticles B-nanoparticle to form an entangled matrix like those of nanofilament - based hydrogels . [SEP]

[CLS] there have been a number of reports that feature multicomponent hydrogels , formed through the interaction of two or more species . [SEP]

[CLS] when ding and coworkers attempted to use the peptide B-material nap - gffygrgd to encapsulate the anticancer B-property drug dox , they were surprised to find that it could form a hydrogel . [SEP]

[CLS] the peptide B-material alone forms nanofilaments but is unsuitable for gel formation due to poor inter - fiber interactions , though has shown utility the encapsulation of hydrophobic B-property drugs . [SEP]

[CLS] instead of drug encapsulation , however , they found that dox formed large nanospheres B-nanoparticle ( ~ 150 nm in diameter ) on the fiber surface , essentially acting as cross - linkers between neighboring fibers and thus enabling gel formation ( fig . 9d ) . [SEP]

[CLS] drug release was observed to be faster from weaker gels ; thereby correlating with the dox concentration of the hydrogels , with higher concentrations giving stronger gels . [SEP]

[CLS] another example is provided by the shi lab , who adopted a highly supramolecular approach ( fig . 9e ) . [SEP]

[CLS] conjugating a low molecular weight peg chain to cpt , they then mixed a solution of this micelleforming conjugate with - cyclodextrin ( - cd ) , a cyclized glucose hexamer with a central hydrophobic B-property cavity . [SEP]

[CLS] multiple - cd molecules thread onto the extended peg chains to form what is known as a polypseudorotaxane , with interactions between - cd units then acting to cross - link the micelles B-material and form a hydrogel matrix . [SEP]

[CLS] while not a strong gel , it did exhibit shear thinning behavior that would make it suitable for injectable administration . [SEP]

[CLS] furthermore , this gel could encapsulate the water soluble anticancer B-property drug , 5 B-material - I-material fluorouracil I-material ( 5 - fu ) , which is often used in combination with cpt , with no disruptive effect on the hydrogel . [SEP]

[CLS] this three - component system displayed superior in vitro anticancer B-property activity when compared to each drug alone , suggesting a synergetic effect of the two drugs , though only at low 5 - fu concentrations as higher concentrations resulted in an antagonistic effect that is known for this drug combination . [SEP]

[CLS] in a final example , jana and dastidar developed a xerogel platform in which naproxen and its - alanine B-material derivatives were induced to form gels by the addition of the biocompatible B-property amine B-material , serinol . [SEP]

[CLS] the resulting salt B-material could form an extended hydrogen B-material bonding network , giving nanofibers B-nanoparticle that could entangle to form gels with weak to moderate mechanical properties . [SEP]

[CLS] a topical gel formulation was prepared and used to successfully treat chemically - induced psoriasis - like inflammation in mice . [SEP]

[CLS] gel treated mice completely recovered within 14 days , including hair regrowth , while those in the control group died after 2 days . [SEP]

[CLS] supramolecular hydrogels formed by amphiphilic B-property prodrugs are well positioned to become a successful nanomedicine , particularly given the wide usage of conventional hydrogels in clinical treatments . [SEP]

[CLS] this platform can potentially be applied to many disease areas due to the broad range of drug classes that can be converted into hydrogelating materials . [SEP]

[CLS] before this can come to fruition , however , more in vivo studies are required to ascertain just how these supramolecular materials will function in a physiological environment . [SEP]

[CLS] the mechanical properties of these materials are important in this context as shear stresses both during and after administration may affect the integrity of the gel and lead to a faster rate of drug release or even gel clearance . [SEP]

[CLS] release of the drug is another critical function of hydrogels , if the gel is too stable then the release may be slower than desired and result in poor efficacy . [SEP]

[CLS] if it is to be triggered by a particular chemical or biological entity rather than simple hydrolysis , then the gel must be sufficiently permeable to that stimulus . [SEP]

[CLS] a balance is therefore necessary with regard to the mechanical properties , and it is clear from the work reported that the drug can have a strong influence on the gel strength . [SEP]

[CLS] accordingly , strategies must be devised to address any issues that may arise for a particular drug class in order to develop the most effective therapeutic hydrogel possible . [SEP]

[CLS] utilizing drugs as building units for the construction of nanostructures represents a paradigm shift in the growing field of nanomedicine , one in which drugs are no longer considered as passive cargos but as active participants in their own delivery to therapeutic targets . [SEP]

[CLS] by exploiting the molecular properties that drug molecules possess in the context of self - assembly and combining them with complementary entities , it is now possible to construct discrete nanostructures that possess a high and precisely defined drug content through rational molecular design . [SEP]

[CLS] three main strategies have emerged to accomplish this , each having their own unique advantages and disadvantages . [SEP]

[CLS] for instance , while macromolecular amphiphilic B-property prodrugs are the most well - developed of the three due to their similarity with other polymer - based delivery systems , the prevalence of spherical nanostructures may limit their use and optimization to address the sophisticated challenges associated with systemic delivery applications . [SEP]

[CLS] conversely , supramolecular hydrogels formed by amphiphilic B-property prodrugs are ideally suited to local delivery for treating cancers or other diseases that can benefit from topical or local administration of therapeutics . [SEP]

[CLS] amphiphilic B-property prodrugs straddle the line between maps and hydrogelators , with their tunable morphologies enabling the adaptation for either route of administration . [SEP]

[CLS] however , it has yet to be established how adaptable this platform is due to the strong influence of the drug molecule as a structural element and the limited number of drug structures tested so far . [SEP]

[CLS] given the push towards personalized medicine that is currently underway , it is important that the principles underlying how a drug molecule can affect the assembly of a nanostructure are determined and understood . [SEP]

[CLS] the drug delivery community as a whole would benefit greatly from the availability of generic platforms that can deliver a particular drug type . [SEP]

[CLS] after all , even though medicines may become personalized , they will still need to be effectively delivered to target sites so as to exert the desired biological effects . [SEP]

[CLS] for all systems , a big question to be answered is how will the physiological environment impact the physicochemical properties and eventually the performance of these drug - containing nanostructures ? [SEP]

[CLS] how is the integrity of the nanostructures affected by interactions with proteins B-material and the body ' s natural defense systems ? [SEP]

[CLS] part of this lies with the critical aggregation concentration of the self - assembled nanostructure , for which a careful balance is required as too low a value may impede the drug release , while too high will lead to rapid dissociation . [SEP]

[CLS] the latter is clearly undesirable for the purpose of systemic delivery , but could be an advantageous property for local delivery , particularly if the dissociation kinetics can be used to tune the drug release rate . [SEP]

[CLS] for systemic delivery , if the goal is to reduce the cac as much as possible , then strategies to facilitate dissociation at the desired location must also be considered in parallel . [SEP]

[CLS] one potential method is the inclusion of self - immolating components that will breakdown in specific environments , thereby negating the need for equilibrium driven dissociation . [SEP]

[CLS] while many challenges are still ahead , the direct use of drugs to build well - defined nanostructures presents a significant extension from both fields of molecular assembly and medicine . [SEP]

[CLS] aside from a few examples formed from macromolecular amphiphilic B-property prodrugs that have been evaluated in clinical trials , those created by assembly of small molecular amphiphilic B-property prodrugs are still focused on fundamental studies of their assembly behavior and in vitro evaluation of their potency against cancer cell B-material lines . [SEP]

[CLS] clearly , the next logical step will be testing these supramolecular materials in animals to collect information on their circulation fate and therapeutic efficacy , which will prove essential for guiding the design of next generation of drug - containing nanostructures for improved performance . [SEP]

[CLS] introducing greater complexity into macromolecular amphiphile B-property prodrugs . [SEP]

[CLS] ( a ) liu ' s approach utilizes a photo - caged poly - cpt - containing map coassembled with a folic B-material acid I-material conjugated polymer B-material to form a micelle B-material that was then cross - linked with an acid - and reduction - sensitive linker . [SEP]

[CLS] reprinted with permission from ref , copyright 2013 american chemical society . [SEP]

[CLS] ( b ) chilkoti ' s elp - based delivery platform that assembles into micelles B-material ( c ) when conjugated to doxorubicin B-material . [SEP]

[CLS] in vivo visualization of the phase transition that occurs on heating of the tumor B-material vasculature from 37°c ( d ) to 42°c ( e ) , indicating the increased accumulation of doxorubicin B-material within the vasculature after thermal cycling . [SEP]

[CLS] panels b - c were adapted with permission from ref , copyright 2009 nature publishing group ; panels d - e were adapted with permission from ref , copyright 2014 american chemical society . [SEP]

[CLS] futher interactions between these nanospheres B-nanoparticle induces the formation of a weak gel . [SEP]

[CLS] adapted with permission from ref , copyright 2011 royal society of chemistry . [SEP]

[CLS] ( d ) schematic illustration of xue ' s platform , in which a non - gelating peptide B-material is induced to form a hydrogel through the formation of doxorubicin B-material nanospheres B-nanoparticle that act as cross - linkers between filaments . [SEP]

[CLS] reprinted with permission from ref , copyright 2015 nature publishing group . [SEP]

[CLS] ( e ) schematic illustration of the highly supramolecular approach adopted by shi , in which cpt - peg micelles B-material form polypseudorotaxane structures via threading of - cyclodextrin onto one or more peg chains , thereby cross - linking and triggering gel formation . [SEP]

[CLS] the drug 5 B-material - I-material fluorouracil I-material ( 5 - fu ) could also be encapsulated within the gel , with the slow dethreading of the psuedorotaxane breaking down the gel and releasing 5 - fu and peg - cpt micelles B-material , that then underwent hydrolysis to release cpt . [SEP]

[CLS] reprinted from ref , copyright 2013 royal society of chemistry . [SEP]

[CLS] figures [SEP]

[CLS] 1 molecular structures of some small molecule drugs with the potential for self - association into molecular clusters or discrete nanostructures . [SEP]

[CLS] 2 representative transmission B-technique electron I-technique microscopy I-technique ( tem ) images of discrete nanostructures formed by the assembly of pure drugs . [SEP]

[CLS] ( a ) cui and coworkers demonstrated how folic B-material acid I-material could be induced to form nanofilamentous nanostructures by the addition of water B-material to a solution in meoh . [SEP]

[CLS] adapted with permission from ref [ 43 ] , copyright 2013 royal society of chemistry . [SEP]

[CLS] ( b ) hao characterized helical nanoribbons formed by camptothecin . [SEP]

[CLS] adapted with permission from ref [ 45 ] , copyright 2014 royal society of chemistry . [SEP]

[CLS] ( c - d ) yan and coworkers developed an irinotecan - chlorambacil ( ir - cb ) drug - drug conjugate ( c ) that could assemble into nanoparticles B-nanoparticle ( d ) . [SEP]

[CLS] adapted with permission from ref [ 46 ] , copyright 2014 american chemical society . [SEP]

[CLS] 3 macromolecular amphiphilic B-property prodrug platform developed by yokoyama and kataoka . [SEP]

[CLS] ( a ) peg - p ( asp ( adr ) ) for the delivery of doxorubicin B-material and ( b ) pt cross - linked peg - p ( glu ) polymer B-material for the delivery of cisplatin B-material upon ligand exchange . [SEP]

[CLS] panel b was adapted with permission from ref [ 67 ] , copyright 1996 elsevier . [SEP]

[CLS] 4introducing greater complexity into macromolecular amphiphile B-property prodrugs . [SEP]

[CLS] ( a ) liu ' s approach utilizes a photo - caged poly - cpt - containing map coassembled with a folic B-material acid I-material conjugated polymer B-material to form a micelle B-material that was then cross - linked with an acid - and reduction - sensitive linker . [SEP]

[CLS] reprinted with permission from ref , copyright 2013 american chemical society . [SEP]

[CLS] ( b ) chilkoti ' s elp - based delivery platform that assembles into micelles B-material ( c ) when conjugated to doxorubicin B-material . [SEP]

[CLS] in vivo visualization of the phase transition that occurs on heating of the tumor B-material vasculature from 37°c ( d ) to 42°c ( e ) , indicating the increased accumulation of doxorubicin B-material within the vasculature after thermal cycling . [SEP]

[CLS] panels b - c were adapted with permission from ref , copyright 2009 nature publishing group ; panels d - e were adapted with permission from ref , copyright 2014 american chemical society . [SEP]

[CLS] 5 a self - assembling drug amphiphile B-property platform developed by cui and coworkers . [SEP]

[CLS] ( a ) the generic design of the drug amphiphile B-property , illustrating the essential features : a hydrophobic B-property drug , cleavable linker and a short peptide B-material with overall hydrophilicity B-property and a strong preference for a particular secondary structure . [SEP]

[CLS] a branching point allows attachment of multiple drug molecules . [SEP]

[CLS] ( b ) molecular structure of a cpt - containing drug amphiphile B-property , mcpt - buss - tau , comprising a reduction - sensitive linker and a sheet forming tau peptide B-material . [SEP]

[CLS] ( c - e ) representative tem images of the drug amphiphiles B-property mcpt - buss - tau ( c ) , dcpt - buss - tau ( d ) , and qcpt - buss - tau ( e ) . [SEP]

[CLS] white arrows represent the open ends of the nanotubes B-nanoparticle formed by qcpt - buss - tau . [SEP]

[CLS] ( f ) schematic illustration of how assembled drug amphiphiles B-property can act as drug reservoirs , with the assembled form protecting the linker from premature cleavage . [SEP]

[CLS] dissociation of the nanostructure releases the single molecule form which is vulnerable to [SEP]

[CLS] 6 construction of interesting architectures through the manipulation of the molecular packing . [SEP]

[CLS] ( a - b ) representative tem images of a dual drug amphiphile B-property containing both cpt and ptx , indicating the structural evolution of cpt - ptx - sup35 , which initially forms a mixture of small , flexible filaments and two - filament twisted fibrils ( a ) , but after 24 h the two - filament twisted fibril nanostructure is the only structure observed ( b ) . [SEP]

[CLS] adapted with permission from ref [ 106 ] , copyright 2014 royal society of chemistry . [SEP]

[CLS] ( c ) cryogenic tem image of a catanionic mixture of two oppositely charged drug amphiphiles B-property , showing the formation of form large multiwalled nanotubes B-nanoparticle . [SEP]

[CLS] adapted from ref [ 110 ] , copyright 2014 royal society of chemistry . [SEP]

[CLS] 7 alternate approaches to the creation of amphiphilic B-property prodrugs . [SEP]

[CLS] ( a ) grinstaff and parquette ' s di - lysine - based cpt conjugate that can assemble into large nanotubes B-nanoparticle via the formation and maturation of helical tape structures . [SEP]

[CLS] adapted with permission from ref [ 117 ] , copyright 2015 wiley - vch . [SEP]

[CLS] ( b - d ) dna - drug amphiphile B-property platform . [SEP]

[CLS] schematic illustration of the molecular structure , assembly and degradation of dna - drug amphiphile B-property ( b ) . [SEP]

[CLS] representative tem images of the spherical nanostructure formed by dna5 - cpt in phosphate - buffered saline ( pbs ) ( cb ) and the rod - like structure formed by dna20 - cpt in pbs with 5 mm mgcl2 ( d ) . [SEP]

[CLS] adapted from from ref [ 177 ] , copyright 2015 american chemical society . [SEP]

[CLS] 8 examples of peptide B-material - based molecular hydrogelators . [SEP]

[CLS] ( a - b ) peptide B-material - based drugs that are capable of forming hydrogels either by themselves ( autogels ) ( a ) or by the addition of a hydrophobic B-property moiety to induce gelation ( b ) . [SEP]

[CLS] panel b was adapted with permission from ref [ 141 ] , copyright 2002 american chemical society . [SEP]

[CLS] ( c ) xu ' s taxol - based hydrogelator , nap - ffk ( succ - ptx ) py , for which the phosphatase - catalysed removal of a tyrosine B-material phosphate group decreases the solubility B-property , triggering nanofilament B-nanoparticle formation and ultimately gelation via entanglement . [SEP]

[CLS] adapted with permission from ref , copyright 2009 american chemical society . [SEP]

[CLS] ( d ) yang ' s dual drug containing hydrogelator , in which an anticancer B-property drug ( ptx or hcpt ) is paired with the anti B-property - I-property inflammatory I-property / immunosuppressant , dexamethasome ( dex ) . [SEP]

[CLS] gelation is triggered by the reduction of the disulfide bond that is used to attach a hydrophilic B-property tail . [SEP]

[CLS] adapted with permission from ref , copyright 2012 royal society of chemistry . [SEP]

[CLS] 9 alternate approaches to the creation of molecular hydrogelators . [SEP]

[CLS] ( a - c ) yang ' s folic B-material acid I-material ( fa ) - taxol based hydrogelator ( a ) that forms nanospheres B-nanoparticle rather than nanofilaments , as indicated by atomic B-technique force I-technique microscopy I-technique ( afm ) ( b ) , through hoogsteen hydrogen B-material bonding between fa molecules ( c ) . [SEP]

[CLS] futher interactions between these nanospheres B-nanoparticle induces the formation of a weak gel . [SEP]

[CLS] adapted with permission from ref , copyright 2011 royal society of chemistry . [SEP]

[CLS] ( d ) schematic illustration of xue ' s platform , in which a non - gelating peptide B-material is induced to form a hydrogel through the formation of doxorubicin B-material nanospheres B-nanoparticle that act as cross - linkers between filaments . [SEP]

[CLS] reprinted with permission from ref , copyright 2015 nature publishing group . [SEP]

[CLS] ( e ) schematic illustration of the highly supramolecular approach adopted by shi , in which cpt - peg micelles B-material form [SEP]

[CLS] the surface properties of nanoparticles B-nanoparticle ( nps B-nanoparticle ) dictate their interaction with the outside world . [SEP]

[CLS] the use of precisely designed molecular ligands to control np B-nanoparticle surface properties provides an important toolkit for modulating their interaction with biological systems , facilitating their use in biomedicine . [SEP]

[CLS] in this review we will discuss the application of the atom - by - atom control provided by organic synthesis to the generation of engineered B-nanoparticle nanoparticles I-nanoparticle , with emphasis on how the functionalization of nps B-nanoparticle with these " small " organic molecules ( mw < 1 , 000 ) can be used to engineer nps B-nanoparticle for a wide range of applications . [SEP]

[CLS] fabricating nanoparticles B-nanoparticle ( nps B-nanoparticle ) with unique biological properties is a challenging but rewarding task . [SEP]

[CLS] the combination of multiple np B-nanoparticle features such as core B-material size , [SEP]

[CLS] shape , and surface chemistry [SEP]

[CLS] allows the regulation of the biological behavior . [SEP]

[CLS] the np B-nanoparticle surface is the interface with the outside world , and plays a prominent role in the interaction with biomolecules . [SEP]

[CLS] the relatively large surface area of nps B-nanoparticle facilitate the attachment of a wide range of biomacromolecules such as peptides B-material , proteins B-material , nucleic B-material acids I-material , and viruses to dictate np B-nanoparticle - protein or np B-nanoparticle - cell B-material interactions . [SEP]

[CLS] likewise , polymers B-material have been widely employed as np B-nanoparticle coverages . [SEP]

[CLS] the structural complexity and / or potential biodegradability B-property of these macromolecular systems , however , introduce complexity to the interactions between nps B-nanoparticle and biomolecules . [SEP]

[CLS] the use of non - polymeric " small " organic molecules provides a robust and scalable methodology to tailor the nano - bio interface . [SEP]

[CLS] the wide variety of moieties available through organic chemistry provides a rich toolkit to provide atom - by - atom control of the np B-nanoparticle - biomolecule interactions . [SEP]

[CLS] in this review we will present research focusing on controlling the interactions of nps B-nanoparticle with proteins B-material and cells B-material by using these " small " molecule ( mw < 1 , 000 ) ligands . [SEP]

[CLS] the interaction modes of nps B-nanoparticle with proteins B-material and cells B-material can be modified by designing the surface monolayer , concomitantly modulating biological functions . [SEP]

[CLS] 24 this fine - tuned control provides a finely - honed tool for a wide array of biological interactions . [SEP]

[CLS] modulating enzyme - nanoparticle B-nanoparticle interactions . [SEP]

[CLS] engineered interactions between nps B-nanoparticle and enzymes provide tools for both enhancing enzyme stability and regulating activity . [SEP]

[CLS] decorating nps B-nanoparticle with engineered ligands facilitates the ' dialing in ' of specific modes of interaction including electrostatic , hydrogen B-material bonding , and van der waals forces . [SEP]

[CLS] this capability has been demonstrated using anionic gold B-nanoparticle nanoparticles I-nanoparticle ( aunps B-nanoparticle ) and chymotrypsin ( cht ) , utilizing the positive " patch " around the cht active site . [SEP]

[CLS] the studies demonstrated that the anionic surface of nps B-nanoparticle can selectively recognize this cationic B-material patch , thus inhibiting cht activity . [SEP]

[CLS] similarly , a variety of amino acid - terminated ligands bearing tunable charge and hydrophobicity B-property ( fig . 1 ( a ) ) provided detailed information about np B-nanoparticle - cht interfacial recognition . [SEP]

[CLS] a thorough examination of the binding constants revealed that aunps B-nanoparticle bearing hydrophobic B-property groups bind more strongly to cht than aunps B-nanoparticle with hydrophilic B-property groups , indicating the importance of hydrophobic B-property interactions I-property at the interface ( fig . 1 ( b ) ) . [SEP]

[CLS] in addition to hydrophobicity B-property , the chirality of the amino B-material acids I-material is also an important factor for the affinity of nps B-nanoparticle and proteins B-material . [SEP]

[CLS] these results demonstrate that very specific chemical features can be employed to modulate protein B-material recognition . [SEP]

[CLS] furthermore , these studies also evidenced that unlike small molecule enzyme regulators , the binding affinity of nps B-nanoparticle to enzymes is not the only factor that modifies the catalytic activity . [SEP]

[CLS] the work from rotello et al . showed that the reduction of enzymatic activity mediated by nps B-nanoparticle was also observed when nps B-nanoparticle were functionalized with hydrophilic B-property ligands because of the denaturation of cht caused by these functional groups ( fig . 1 ( c ) and ( d ) ) . [SEP]

[CLS] likewise , hamad - schifferli et al . reported that irreversible denaturation of glucose oxidase ( gox ) caused by the interaction with nps B-nanoparticle had a negative effect on its enzymatic activity . [SEP]

[CLS] recently , das et al . reported that nps B-nanoparticle can also improve enzymatic activity . [SEP]

[CLS] their investigation on the activity of mitochondrial membrane cytochrome c ( cyt c ) bound with cationic B-material nps B-nanoparticle demonstrated the enhanced peroxidase activity by increasing hydrophobicity B-property of nps B-nanoparticle . [SEP]

[CLS] structural reorganization caused by hydrophobic B-property nps B-nanoparticle exposed the heme B-material group I-material of the enzyme , facilitating substrate access to the catalytic site . [SEP]

[CLS] in stark contrast to their ability to denature protein B-material , functionalized nps B-nanoparticle have been used as synthetic chaperones that assist in the refolding of denatured enzymatic proteins B-material . [SEP]

[CLS] for instance , fully recovery of enzymatic activity of thermally denatured cationic B-material proteins B-material such as cht and papain has been observed using malonic acid - functionalized anionic aunps B-nanoparticle followed by disruption of the protein - np B-nanoparticle complex with aqueous sodium B-material chloride I-material . [SEP]

[CLS] enzymatic activity can also be modified by using the nps B-nanoparticle functionalized with specific small molecule enzyme inhibitors or activators . [SEP]

[CLS] supuran and co - workers coated aunps B-nanoparticle with an inhibitor of carbonic anhydrase ( ca ) , and the np B-nanoparticle displayed higher selectivity toward tumor associated isoform ix over the cytosolic isozymes i and iiix . [SEP]

[CLS] likewise , ca showed increased enzymatic activity when mixed with nps B-nanoparticle bearing a ca activator . [SEP]

[CLS] these studies show functionalization on np B-nanoparticle surface can modulate the activity B-property of I-property small I-property molecule I-property enzyme regulators , providing a new platform for the enzyme regulation . [SEP]

[CLS] correlation between the denaturation rate constants ( k ) of cht and the hydrophobicity B-property index of amino B-material acid I-material side chains in nanoparticles B-nanoparticle . [SEP]

[CLS] reprinted with permission from . [SEP]

[CLS] modulation of protein - protein interactions . protein - protein interactions ( ppi ) play a central role in numerous cellular B-event processes I-event including apoptosis B-event and angiogenesis B-event , thus targeting theinterface between proteins B-material provides a potential way for treating diseases . [SEP]

[CLS] however , due to the large contact area between proteins B-material in these complexes , effective inhibition of ppis is quite challenging . [SEP]

[CLS] knapp and rotello reported that charged aunps B-nanoparticle can inhibit the recognition of cyt c with cytochrome c peroxidase ( cpp ) ( fig . 2 ) . [SEP]

[CLS] since this ppi is defined by saltbridges between the cationic B-material surface of cyt c and the anionic surface of cpp , they designed aunps B-nanoparticle with cationic B-material , neutral , or anionic aunps B-nanoparticle , and examined charge dependent inhibition of ppi . [SEP]

[CLS] as a result , effective disruption of the cyt c - cpp complex was observed only when charged nps B-nanoparticle were used , while neutral nps B-nanoparticle had no effect . [SEP]

[CLS] notably , because of the multivalency of nps B-nanoparticle , a single np B-nanoparticle could interact with more than one protein B-material , implying that nps B-nanoparticle could be effective modulators that can disrupt multiple ppis . [SEP]

[CLS] minimizing nonspecific np B-nanoparticle - protein B-material interactions . [SEP]

[CLS] minimizing interactions between nanoparticles B-nanoparticle and proteins B-material is also an important challenge for a diversity of biological applications . [SEP]

[CLS] for example , when nps B-nanoparticle are intended for biomedical imaging or as therapeutic agents , the adsorption and denaturation of proteins B-material over the np B-nanoparticle surface induces a rapid elimination of the from the body . [SEP]

[CLS] this phenomenon critically reduces the efficacy of the engineered delivery vehicles B-material and targeted nps B-nanoparticle . [SEP]

[CLS] the classical approach to provide " non - interacting " capabilities to the nps B-nanoparticle is the use of oligo ( ethylene glycol ) ( oeg ) functionalities , which reduces protein B-material denaturation over the np B-nanoparticle surface . [SEP]

[CLS] this is translated into longer blood circulation times comparative to other systems , achieving higher tumor B-material accumulation rates . [SEP]

[CLS] however , oeg functionalized nps B-nanoparticle undergo a process known as accelerated blood clearance ( abc ) , a phenomenon that increases the elimination of the nps B-nanoparticle after the second dose due to the formation of antibodies B-material against the probe . [SEP]

[CLS] an alternative to oeg functionalization is the use of zwitterionic molecules based principally on two chemical structures , namely betaines and amino B-material acids I-material . [SEP]

[CLS] the zwitterionic nature of those structures confers strong non - fouling properties to nps B-nanoparticle . [SEP]

[CLS] as an example , it has been reported that small aunps B-nanoparticle ( ~ 5 nm , high area / volume ratio ) coated with a mixture of citrate and cysteine B-material do not absorb proteins B-material even at physiological serum concentrations ( fig . 3 ) . [SEP]

[CLS] in addition , functionalized quantum B-nanoparticle dots I-nanoparticle ( 3 . 4 nm ) with cysteine B-material and tumor B-material targeting groups have exhibited significantly lower renal clearance rates as well as the high tumor B-material targeting efficiency ( fig . 4 ) . the derivatization of ligands using amino B-material acids I-material , however , is limited by the fact that neutral charge is desirable for the stealth capabilities , and the addition of more amino B-material acids I-material may modify this property . [SEP]

[CLS] betaines , on the other hand , come in a myriad of structures ( carboxybetaines , phosphobetaines , sulfobetaines ) and they have been shown to enhance the stealth properties of nps B-nanoparticle such as reduced protein B-material adsorption , longer blood circulation time and low clearance . [SEP]

[CLS] in addition , betaines are easily modified by changing the substituents over the ammonium group without affecting the overall neutral charge . [SEP]

[CLS] a final method to obtain zwitterionic properties at the np B-nanoparticle surface is the use of a mixed monolayer nps B-nanoparticle containing both cationic B-material and anionic ligands . [SEP]

[CLS] by adjusting the ratio of those ligands during the place exchange reaction , the zero net charge can be achieved . [SEP]

[CLS] although this technique has also rendered nps B-nanoparticle with strong non - fouling properties , reproducibility is still a challenge . [SEP]

[CLS] reprinted with permission from . [SEP]

[CLS] the cellular adsorption and internalization of nps B-nanoparticle are predominantly determined by their surface charge . [SEP]

[CLS] multiple reports demonstrate a significant difference on the cellular uptake rate between positively charged nps B-nanoparticle and other charged nps B-nanoparticle ( negative , neutral , and zwitterionic ) ( fig . 5 ) ] . [SEP]

[CLS] the strong electrostatic interaction between the negatively charged cell B-material membranes and cationic B-material nps B-nanoparticle is the underlying factor that increases the amount of nps B-nanoparticle adsorbed onto the cell B-material surface , thus enhancing cellular uptake . [SEP]

[CLS] however , in some case , the strong cellular uptake was observed with negatively charged nanoparticles B-nanoparticle . [SEP]

[CLS] the studies demonstrated that iron B-material oxide I-material ( fe2o3 ) nanoparticles B-nanoparticle functionalized with carboxylate B-material group I-material can be efficiently taken up by cancer cell B-material lines presumably because of the direct diffusion through membrane or the pinocytosis of anionic nanoparticles B-nanoparticle . [SEP]

[CLS] in addition to the surface charge , the hydrophobicity B-property of nps B-nanoparticle can also be employed to modify the cellular uptake of these materials . [SEP]

[CLS] a study using cationic B-material nps B-nanoparticle demonstrated that an increase of the aunp B-nanoparticle surface hydrophobicity B-property enhances cellular uptake in the absence of serum , while it decreases uptake in the presence of serum . [SEP]

[CLS] the binding B-event of I-event serum I-event proteins I-event to aunps B-nanoparticle is influenced by the surface charge and hydrophobicity B-property , compromising the np B-nanoparticle uptake . [SEP]

[CLS] there are some efforts to enhance the cellular uptake of zwitterionic aunps B-nanoparticle by using hydrophobicity B-property , demonstrating slightly higher cellular uptake of hydrophobic B-property aunps B-nanoparticle compared with hydrophilic B-property counterparts , either in the presence or absence of serum proteins B-material . [SEP]

[CLS] the binding mode between ligand and nanoparticle B-nanoparticle surface can affect the cellular interaction . [SEP]

[CLS] cell B-material experiments using cationic B-material quantum B-nanoparticle dots I-nanoparticle bearing monothiol or dithiol coordination groups revealed a significant difference on the cellular uptake of nanoparticles B-nanoparticle ( fig . 6 ) . [SEP]

[CLS] these results indicate the importance of molecular design that considers not only effects from the headgroups but also effects from the overall ligand design . [SEP]

[CLS] uptake of quantum B-nanoparticle dots I-nanoparticle after the incubation B-technique with hela cells B-material . [SEP]

[CLS] reprinted with permission from . [SEP]

[CLS] in addition to " permanent " physicochemical properties , a chemical designing approach can also construct " responsive " surfaces that can alter the physicochemical features of the nps B-nanoparticle by endogenous stimuli . [SEP]

[CLS] such chemical surfaces generate unique interaction modes with biological systems . [SEP]

[CLS] ph - responsive aggregate formation . [SEP]

[CLS] enhancing cellular uptake with stimuli responsive np B-nanoparticle surfaces was initially reported by the kim group . [SEP]

[CLS] negatively charged citraconic amide functionalized " smart " aunps B-nanoparticle form aggregates upon exposure to weakly acidic environments ( ph = 5 . 5 ) ( fig . 7 ( a ) and ( b ) ) . [SEP]

[CLS] acid induced partial cleavages of citraconic amide B-material group I-material and subsequent exposure of cationic B-material primary B-material amine I-material neutralize the surface charge of nps B-nanoparticle , inducing aggregation . [SEP]

[CLS] aunps B-nanoparticle are exposed to acidic endosomal environments during cellinternalization process . [SEP]

[CLS] when an aggregate is formed inside an endosome , the exocytosis of aunps B-nanoparticle is blocked , resulting in a larger amount of aunps B-nanoparticle accumulated in b16f10 cells B-material compared to negatively charged aunps B-nanoparticle used as controls ( fig . 7 ( c ) ) . [SEP]

[CLS] aunps B-nanoparticle bearing a mixed monolayer of quaternary ammonium and carboxylic B-material acid I-material ligands can provide high tunable ph - induced aggregation systems . [SEP]

[CLS] partial protonation of carboxylate B-material functionality at acidic ph can induce the aggregate formation by the neutralization of surface charge . [SEP]

[CLS] the ph value at which nps B-nanoparticle form aggregates can be tuned by changing the surface ligand coverage ratio and core B-material size . [SEP]

[CLS] ji et al . applied this system for tumor B-material targeting , utilizing the ph difference between tumor B-material tissue ( ph 6 . 0 - 6 . 6 ) and normal tissue ( ph 7 . 4 ) as a tumor B-material environment signal . [SEP]

[CLS] mixing the same mole ratio of cationic B-material and anionic ligands with 16 nm aunps B-nanoparticle , they constructed aunps B-nanoparticle that form aggregates at ph 6 . 5 ( fig . 8 ( a ) and ( b ) ) . [SEP]

[CLS] in vitro cellular uptake studies demonstrated that a ph decrease enhanced np B-nanoparticle internalization ( fig . 8 ( c ) ) due to the accelerated sedimentation of aunps B-nanoparticle . [SEP]

[CLS] subsequent in vivo studies indicated the enhancement of tumor B-material accumulation and retentions of these aunps B-nanoparticle ( fig . 8 responsive surface which can reversibly switch from zwitterionic into cationic B-material . [SEP]

[CLS] the chemical moiety at the surface features alkoxyphenyl acylsulfonamide groups that is protonated under weakly acidic conditions ( fig . 9 ( a ) ) . [SEP]

[CLS] aunps B-nanoparticle functionalized with this ph - responsive zwitterionic group exhibited neutral zeta B-property - potential I-property at ph 7 . 4 and showed a sharp response to ph decrease , switching into cationic B-material at ph 6 . 6 and 6 . 0 without forming aggregates ( fig . 9 ( b ) ) . [SEP]

[CLS] as discussed previously , aunps B-nanoparticle with cationic B-material ligands are prone to be adsorbed by the negatively charged cell B-material membranes , resulting in higher cellular uptake than that of zwitterionic aunps B-nanoparticle . [SEP]

[CLS] cell B-material studies indicated that the ph - responsive zwitterionic surface does induce an enhancement in cellular uptake of aunps B-nanoparticle by cancerous cells B-material at tumor B-material ph ( 6 . 6 - 6 . 0 ) , achieving a four - fold increase at ph 6 . 0 compared to the cellular uptake at ph 7 . 4 . [SEP]

[CLS] on the other hand , a nonresponsive alkyl analogue did not show differences over the ph range studied ( fig . 9 ( c ) ) . [SEP]

[CLS] this result indicates that subtle structural differences of zwitterionic moieties could generate a targeting function for selective accumulation of aunps B-nanoparticle in tumor B-material tissues . [SEP]

[CLS] esterase - induced cellular uptake of amphiphilic B-property aunp B-nanoparticle . [SEP]

[CLS] ph is not the only stimulus to enhance the interaction between nps B-nanoparticle and cells B-material . [SEP]

[CLS] niikura and coworkers demonstrated that an esterase - catalyzed hydrolysis of ester moieties can be used as to enhance the cellular uptake of amphiphilic B-property aunps B-nanoparticle . [SEP]

[CLS] 10 nm aunps B-nanoparticle were functionalized with ester or ether - headed amphiphilic B-property peg ligands which enable nps B-nanoparticle to dissolve both of polar B-material and nonpolar solvents I-material through systematic conformational changes ( fig . 10 ( a ) and ( b ) ) . [SEP]

[CLS] investigation of the cellular internalization of those aunps B-nanoparticle revealed that aunps B-nanoparticle with ester functionalities were taken up by cells B-material in a greater extent than the corresponding ether - aunps B-nanoparticle ( fig . 10 ( c ) ) . [SEP]

[CLS] the authors assumed that even though both ester and ether - headed aunps B-nanoparticle have a high affinity to hydrophobic B-property cell B-material membranes , the exposure of alkyl moieties during the interaction with cells B-material generated an esterase - mediated hydrolysis that enabled longer retention of aunps B-nanoparticle at the cell B-material membrane , accelerating endocytosis B-event ( fig . 10 ( d ) ) . [SEP]

[CLS] 10d is based on information obtained in the report . [SEP]

[CLS] as shown above , surface chemistry defines the interactions of nps B-nanoparticle with biological systems . [SEP]

[CLS] building the surface with proper chemical structures has the potential to overcome many challenges currently present in nanomedicine . [SEP]

[CLS] the examples highlighted in this review clearly show the power of chemical approaches for tailoring the physicochemical properties of nps B-nanoparticle , providing fruitful biological features . [SEP]

[CLS] organic chemistry can be utilized as a " palette " containing an unlimited range of functional groups for the modulation of the np B-nanoparticle functions . [SEP]

[CLS] desired features and functions can be constructed along with the synthesis of functional groups , providing an opportunity of the atom by atom level regulation . [SEP]

[CLS] this approach results in the information of structure - function relationships , providing a deeper understanding of the molecular recognition between nps B-nanoparticle and biological systems as well as bringing along clues on how to control desired effects at specific places . [SEP]

[CLS] such methods will help to maximize the potential of nanomaterials B-material for the creation of novel therapeutics , diagnostics and imaging agents . [SEP]

[CLS] 1 ( a ) structures of amino acid functionalized aunps B-nanoparticle . [SEP]

[CLS] ( b ) correlation between gibbs free energy changes and hydrophobicity B-property index of amino B-material acid I-material side chains . [SEP]

[CLS] ( c ) normalized activity of cht ( 3 . 2 m ) with nanoparticles B-nanoparticle ( 0 . 8 m ) bearing various amino B-material acid I-material side chains . [SEP]

[CLS] ( d ) [SEP]

[CLS] 2 schematic illustration of the interaction between cyt c , ccp , and aunps B-nanoparticle with different surface charge . [SEP]

[CLS] reprinted with permission from [ 42 ] . [SEP]

[CLS] 3 ( a ) chemical structure of citrate and lysine coated aunp B-nanoparticle . [SEP]

[CLS] ( b ) chemical structure of citrate and cysteine coated aunp B-nanoparticle . [SEP]

[CLS] ( c ) dls distributions of citrate and lysine coated aunp B-nanoparticle ( coverage ; lysine B-material / citrate = 1 . 4 ) in water B-material ( green curve ) and fbs ( red curve ) , and citrate aunp B-nanoparticle in fbs ( black curve ) . [SEP]

[CLS] ( d ) dls distributions of citrate and cysteine coated aunp B-nanoparticle ( cysteine B-material / citrate = 1 . 6 ) in water B-material ( green curve ) and fbs ( red curve ) . [SEP]

[CLS] reprinted with permission from [ 49 ] . [SEP]

[CLS] 4 ( a ) chemical structure of zwitterionic quantum B-nanoparticle dots I-nanoparticle bearing targeting groups . [SEP]

[CLS] ( b ) fluorescent B-property images of prostate - specific membrane antigen ( psma ) - positive lncap and psmanegative prostate cancer cells B-material after incubation B-technique with functionalized zwitterionic quantum B-nanoparticle dots I-nanoparticle . [SEP]

[CLS] 5 schematic illustration of the interaction between cell B-material membrane and aunps B-nanoparticle with different surface charge . [SEP]

[CLS] 6 ( a ) chemical structure of mono - and dithiol capped cdse / zns quantum B-nanoparticle dots I-nanoparticle . [SEP]

[CLS] ( b ) [SEP]

[CLS] 7 ( a ) chemical structure of the aunps B-nanoparticle capable of aggregating in acidic ph . [SEP]

[CLS] ( b ) tem images of aunps B-nanoparticle in ph 5 . 5 acetate buffer with different incubation B-technique times of ( i ) 0 , ( ii ) 10 , ( iii ) 30 , ( iv ) 60 , ( v ) 90 min . [SEP]

[CLS] ( c ) dark field microscope images of b16 f10 cells B-material incubated B-technique with " smart " aunps B-nanoparticle ( first column ) , citrate aunps B-nanoparticle ( second column ) , and mua ( 11 - mercaptoundecanoic acid ) - capped aunps B-nanoparticle ( last column ) . [SEP]

[CLS] reprinted with permission from [ 64 ] . [SEP]

[CLS] 3a is based on information obtained in the literature . [SEP]

[CLS] ( d ) and ( e ) ) . [SEP]

[CLS] 8 ( a ) chemical structure of mixed monolayer aunps B-nanoparticle capable of aggregating in acidic conditions . [SEP]

[CLS] ( b ) tem images of aunps B-nanoparticle at ph 7 . 4 and 6 . 5 [ scale bar 50 nm ( upper image ) , 20 nm ( lower image ) ] . [SEP]

[CLS] ( c ) effect of ph on the cellular uptake of aunps B-nanoparticle by hepg2 cells B-material . [SEP]

[CLS] ( d ) comparison of tumor B-material accumulation in kb tumor B-material in balb / c nude mice between ph - responsive aunp B-nanoparticle and peg - functionalized aunp B-nanoparticle . [SEP]

[CLS] ( e ) comparison of tumor B-material tissue retention pattern between ph - responsive aunp B-nanoparticle and peg - functionalized aunp B-nanoparticle . [SEP]

[CLS] reprinted with permission from [ 54 ] . [SEP]

[CLS] 3ais based on information obtained in the literature . [SEP]

[CLS] 9 ( a ) chemical structures of the acylsulfonamide - functionalized ph - responsive and nonresponsive zwitterionic aunps B-nanoparticle , and the mechanism of acidic ph enhanced cellular uptake . [SEP]

[CLS] ( b ) ph dependence of zeta B-property - potential I-property of acylsulfonamide functionalized aunp B-nanoparticle ( c ) effects of ph difference on cellular uptake of aunps B-nanoparticle [SEP]

[CLS] reprinted with permission from . [SEP]

[CLS] 10 ( a ) conformational change of the amphiphilic B-property peg ligands on aunps B-nanoparticle in polar B-material and nonpolar solvents I-material . [SEP]

[CLS] ( b ) chemical structures of the ester and ether - headed amphiphilic B-property peg ligands . [SEP]

[CLS] ( c ) difference of the number of aunps B-nanoparticle taken up by hela cells B-material ( 1 . 0 x 10 5 ) . [SEP]

[CLS] ( d ) esterase - [SEP]

[CLS] nanoparticles B-nanoparticle have been widely studied as versatile platforms for in vivo imaging and therapy . [SEP]

[CLS] however , their use to image and / or treat the brain is limited as they are often unable to cross the blood - brain barrier B-property ( bbb ) . [SEP]

[CLS] to overcome this problem , herein we report the use of focused ultrasound in vivo to successfully deliver dnacoated gold B-nanoparticle nanoparticles I-nanoparticle to specific locations in the brains of mice . [SEP]

[CLS] functionalised metal B-nanoparticle nanoparticles I-nanoparticle that are able to codeliver multiple drugs and / or imaging agents to a target location have attracted great interest in recent years . [SEP]

[CLS] in particular , spherical B-nanoparticle nanoparticles I-nanoparticle coated with a dense layer of oligonucleotides , first pioneered by mirkin et al . , have emerged as promising nanoplatforms for in vivo applications . [SEP]

[CLS] it has been shown that these nanoparticles B-nanoparticle can spontaneously enter over 50 different cell B-material types without the need for an external transfecting agent , have low immunogenicity B-property in cells B-material , good stability and have shown no toxicity B-property so far . [SEP]

[CLS] in addition to this , they are highly versatile , allowing them to be easily tailored for a wide range of applications . [SEP]

[CLS] a variety of core B-material materials can be used to prepare them , ranging from iron B-nanoparticle oxide I-nanoparticle nanoparticles I-nanoparticle to quantum B-nanoparticle dots I-nanoparticle , and almost any oligonucleotide sequence can be attached to the particle surface . [SEP]

[CLS] however , due to their size , the majority of functionalised nanoparticles B-nanoparticle show limited accumulation in the brain due to their inability to cross the blood - brain barrier B-property ( bbb ) . [SEP]

[CLS] this limits their potential application for the imaging and treatment of a range of diseases such as alzheimer ' s disease , parkinson ' s disease and brain tumours . [SEP]

[CLS] as of now , the only way to disrupt the bbb in a non - invasive , transient and targeted manner is with focused ultrasound and microbubbles . [SEP]

[CLS] in this method , microbubbles and the drug of choice are first injected intravenously into the bloodstream . [SEP]

[CLS] the target region is then exposed to ultrasound , which drives the microbubbles into radial oscillation . [SEP]

[CLS] by exerting mechanical stress on the blood vessel walls , an increase in bbb permeability is observed , resulting in enhanced drug delivery . [SEP]

[CLS] the exact biological mechanisms through which this occurs is still under investigation , but it has been linked to a widening of the tight junctions between endothelial cells B-material , increased vesicle activity and a suppression of the drug efflux pumps located at the surface of endothelial cells B-material . [SEP]

[CLS] to date , focused ultrasound - mediated bbb disruption has been successfully used to deliver a wide range of small molecules into the brains of rodents and nonhuman primates . [SEP]

[CLS] in contrast , there are significantly fewer examples where nanoparticles B-nanoparticle have been successfully delivered across the bbb in vivo using focused ultrasound . [SEP]

[CLS] a reason for this is that the dependency of focused ultrasound - mediated delivery on nanoparticle B-nanoparticle diameter has not been previously investigated , making it difficult to design nanoparticles B-nanoparticle for this application : larger nanoparticles B-nanoparticle allow for higher payloads of drug to be delivered to the target location per particle , but may not be delivered as efficiently across the bbb using this technology compared to smaller nanoparticles B-nanoparticle . [SEP]

[CLS] with the aim to address this , herein we report the synthesis of a range of dna - coated gold B-nanoparticle nanoparticles I-nanoparticle ( dna - au nps B-nanoparticle ) of different sizes and show that they can be successfully delivered to specific brain locations across the bbb in mice using focused ultrasound ( figure 1 ) . [SEP]

[CLS] the motivation to carry out this study is to establish a methodology for the future use of nanoparticles B-nanoparticle as delivery vehicles B-material for delivering drugs and / or imaging agents to specific locations in the brain . [SEP]

[CLS] the size - dependency of focused ultrasound - mediated nanoparticle B-nanoparticle delivery across the bbb has also been investigated in this study . [SEP]

[CLS] three sets of au nps B-nanoparticle of different sizes were synthesised via a seeded growth protocol involving the reduction of haucl4 with sodium B-material citrate and traces of tannic acid ( figure 2a ) . [SEP]

[CLS] au nps B-nanoparticle were characterised using dynamic B-technique light I-technique scattering I-technique ( dls ) , transmission B-technique electron I-technique microscopy I-technique ( tem ) and uv - vis spectroscopy B-technique . [SEP]

[CLS] dls measurements and tem images showed that the au nps B-nanoparticle were quasi - spherical in shape and narrowly dispersed , with core B-material diameters of 6 . 3 ± 0 . 7 nm , 9 . 5 ± 1 . 4 nm and 14 . 2 ± 1 . 2 nm ( figure 2b , c and table s1 ) . [SEP]

[CLS] the presence of the characteristic surface plasmon resonance ( spr ) band at ~ 515 nm was observed in the absorption spectra of all au nps B-nanoparticle synthesised ( figure s2 ) . [SEP]

[CLS] moreover , the absorbance and wavelength of the spr band was seen to increase with increasing np B-nanoparticle size as expected . [SEP]

[CLS] synthesised au nps B-nanoparticle were functionalised with cy5 - labelled oligonucleotides to give cy5 - dna - au nps B-nanoparticle a , b and c . [SEP]

[CLS] as previously described by li et al . , tween 20 was first added to stabilise the au nps B-nanoparticle and prevent their aggregation in high ionic strength environments . [SEP]

[CLS] thiolated oligonucleotides were then added to the reaction mixture in the presence of salt B-material to minimise electrostatic repulsions between oligonucleotide strands . a 25 base oligonucleotide sequence was chosen for this study as this is the typical length of oligonucleotides used for gene therapies . [SEP]

[CLS] dls measurements showed that the synthesised cy5 - dna - au nps B-nanoparticle had hydrodynamic diameters of 21 . 6 ± 3 . 3 nm ( a ) , 23 . 3 ± 2 . 6 nm ( b ) and 25 . 2 ± 1 . 9 nm ( c ) respectively ( table 1 ) . [SEP]

[CLS] as expected , changes in the hydrodynamic diameters and zeta B-property potentials I-property were observed after functionalisation with oligonucleotides . [SEP]

[CLS] moreover , the zeta B-property potentials I-property were found to vary between cy5 - dna - au nps B-nanoparticle a , b and c as the oligonucleotide loading was adjusted in each case so that the overall fluorescence B-property intensities were similar to allow for comparison after delivery across the bbb ( figure s3 ) . [SEP]

[CLS] the feasibility of delivering cy5 - dna - au nps B-nanoparticle a - c into the brain in vivo using ultrasound pulses was then assessed . [SEP]

[CLS] wild type c57lb / 6 mice were first injected with sonovue © microbubbles , followed by cy5 - dna - au nps B-nanoparticle a , b or c ( figure 3 ) . [SEP]

[CLS] the left thalamus of the brain was sonicated using ultrasound pulses ( frequency : 1 mhz ; peak - negative pressure : 530 kpa ; pulse length : 10 ms ; pulse repetition frequency : 0 . 5 hz ; sonication duration : 250 s ) , whilst the right thalamus acted as the non - sonicated control . [SEP]

[CLS] following sonication , the brain was extracted , sectioned into 30 μm horizontal sections and then imaged using brightfield and fluorescence B-technique microscopy I-technique . [SEP]

[CLS] evidence of successful bbb disruption in the left thalamus was observed in all experiments conducted . [SEP]

[CLS] due to the characteristic red colour of the au np B-nanoparticle cores B-material , their presence in the left thalamus could be detected in brightfield images ( figure 4 ) . [SEP]

[CLS] fluorescence B-property signal from the attached cy5labelled oligonucleotides was found at the exact same locations , indicating that the cy5 - dna - au nps B-nanoparticle remain intact as they cross the bbb ( figure 4 ) . [SEP]

[CLS] to the best of our knowledge , this is the first time that dna - coated gold B-nanoparticle nanoparticles I-nanoparticle have been delivered across the bbb in vivo using focused ultrasound . [SEP]

[CLS] moreover , in contrast to prior work by jensen et al . in which dna - au nps B-nanoparticle were reported to be able to cross the intact bbb in wild type mice by themselves , no evidence of cy5 - dna - au nps B-nanoparticle a - c was detected in the right thalamus ( control ) in our experiments ( figure 5a ) . [SEP]

[CLS] it should be noted , however , that a lack of fluorescence B-property signal does not indicate that there are no nps B-nanoparticle present ; instead , it might indicate that there are not enough nps B-nanoparticle present to generate a detectable signal . the data presented here therefore shows that focused ultrasound and microbubbles can be used to significantly enhance the delivery of cy5 - dna - au nps B-nanoparticle across the bbb ; furthermore , it allows the directed delivery of nanoparticles B-nanoparticle to specific locations within the brain . [SEP]

[CLS] to investigate the effect of varying np B-nanoparticle diameter on the efficiency of delivery using focused ultrasound - mediated bbb disruption , the normalised optical density - the average fluorescence B-property intensity in the targeted region normalised by the control region - was calculated from the fluorescence B-property images ( figure 5 ) . [SEP]

[CLS] a two - sided student ' s t - test was performed to assess statistical significance . [SEP]

[CLS] our results show that there is a sizedependency associated with the delivery of cy5 - dna - au nps B-nanoparticle across the bbb using focused ultrasound , with the smallest nps B-nanoparticle tested in this study ( a ) being delivered across the bbb six times more efficiently than the largest nps B-nanoparticle tested ( c ) . [SEP]

[CLS] as proposed in the past , the presence of a size - dependency suggests that the enhanced bbb permeability caused by focused ultrasoundmediated bbb disruption is primarily due to enhanced paracellular transport rather than increased vesicular transport as vesicles are much larger than the majority of therapeutic agents . [SEP]

[CLS] it should also be noted that the difference in diameter between cy5 - dna - au nps B-nanoparticle a and c is small ( less than 5 nm ) , suggesting that np B-nanoparticle diameter is an important design criterion to take into account if one wishes to deliver nps B-nanoparticle into the brain using focused ultrasound : whilst larger nps B-nanoparticle offer a greater surface area for the attachment of therapeutic and diagnostic B-property agents I-property , our results show that they are delivered less efficiently than smaller nps B-nanoparticle using the same ultrasound parameters . [SEP]

[CLS] to assess the safety of the focused ultrasound - mediated bbb disruption conducted in this study , brain sections covering the entirety of the focal volume were stained with haematoxylin and eosin ( h & e ) . [SEP]

[CLS] for these experiments , a texas red - labelled 3 kda dextran B-material was injected as a marker of bbb opening and the brain was sonicated using the same ultrasound parameters as above . [SEP]

[CLS] following sonication , mice were immediately sacrificed and brains were extracted for histological analysis . [SEP]

[CLS] in agreement with prior studies , minimal tissue effects were observed , with just a few sites of minor red blood cell B-material extravasation identified in the targeted region ( figure s4 ) . [SEP]

[CLS] in summary , we have shown that dna - au nps B-nanoparticle can be successfully delivered across the bbb using focused ultrasound in a non - invasive and targeted manner . [SEP]

[CLS] moreover , a sizedependency was observed , with smaller nps B-nanoparticle being delivered more efficiently across the bbb using this technology than larger nps B-nanoparticle . [SEP]

[CLS] 1 . schematic representation showing the use of microbubbles and focused ultrasound to deliver dna - coated gold B-nanoparticle nanoparticles I-nanoparticle across the bbb . [SEP]

[CLS] figure 2 . a ) three sets of au nps B-nanoparticle of core B-material diameters 6 . 3 ± 0 . 7 nm , 9 . 5 ± 1 . 4 nm and 14 . 2 ± 1 . 2 nm were synthesised via a seeded growth approach . [SEP]

[CLS] synthesised au nps B-nanoparticle were functionalised with cy5 - labelled oligonucleotides to give cy5 - dna - au nps B-nanoparticle a - c . b ) representative transmission B-technique electron I-technique microscopy I-technique images of au nps B-nanoparticle a - c . [SEP]

[CLS] nanoparticles B-nanoparticle were observed to be quasi - spherical and narrowly dispersed . [SEP]

[CLS] c ) size distribution of au nps B-nanoparticle determined from transmission B-technique electron I-technique microscopy I-technique images . [SEP]

[CLS] a total of 100 nps B-nanoparticle per set were counted using imagej . [SEP]

[CLS] cy5 - dna - au nps B-nanoparticle a - c were successfully delivered to the left thalamus of the brain using focused ultrasound . [SEP]

[CLS] fluorescence B-property signal corresponding to the attached cy5 - labelled oligonucleotides ( red ; cy5 channel ) was found at the exact same locations as signal from the au np B-nanoparticle cores B-material ( blue ; brightfield ) , indicating that the cy5 - dna - au nps B-nanoparticle remain intact as they cross the bbb via focused ultrasound - mediated bbb disruption . [SEP]

[CLS] experimental setup for focused ultrasound - mediated bbb disruption . [SEP]

[CLS] microbubbles are injected intravenously , followed by cy5 - dna - au nps B-nanoparticle a , b or c . [SEP]

[CLS] the left thalamus is sonicated using ultrasound pulses ( frequency : 1 mhz ; peak - negative pressure : 530 kpa ; pulse length : 10 ms ; pulse repetition frequency : 0 . 5 hz ; sonication duration : 250 s ) , whilst the right thalamus acts as the control . [SEP]

[CLS] figure 5 . a ) representative fluorescence B-property images from the delivery of cy5 - dna - au nps B-nanoparticle a - c across the bbb using focused ultrasound . [SEP]

[CLS] a spot - like distribution of fluorescence B-property is observed in the left thalamus , whilst no fluorescence B-property signal is detected in the right thalamus . [SEP]

[CLS] b ) normalised optical density was calculated from fluorescence B-property images as a measure of the nanoparticle B-nanoparticle dose delivered across the bbb ( n = 5 for each set of nps B-nanoparticle ) . [SEP]

[CLS] a size dependency is observed , with the smallest nps B-nanoparticle synthesised ( a ) being delivered six times more efficiently across the bbb using focused ultrasound than the largest nps B-nanoparticle ( c ) ( p < 0 . 05 ) . [SEP]

[CLS] measured [SEP]

[CLS] metal - based anion B-material receptors have several important applications in sensing , separation and transport of negatively charged species . [SEP]

[CLS] amongst these receptors , di - zinc ( ii ) complexes are of particular interest for the recognition of oxoanions , in particular phosphate derivatives . [SEP]

[CLS] herein we report the synthesis of a di - zinc ( ii ) receptor B-material and show that it has high affinity and selectivity for bisphosphonates such as alendronate and etidronatewhich are used to treat a number of skeletal disorders as well as showing interesting anticancer B-property properties . [SEP]

[CLS] the binding mode of the di - zinc ( ii ) receptor B-material with alendronate and etidronate has been unambiguously established by single crystal x - ray crystallography . [SEP]

[CLS] in addition , by modifying the backbone of the receptor B-material , we show that the drug - loaded receptor B-material can be attached onto gold B-nanoparticle nanoparticles I-nanoparticle as potential drug - delivery vehicles B-material . [SEP]

[CLS] over the past two decades , there has been great interest in the development of molecular receptors for oxoanions such as carboxylates B-material , phosphates and nitrates , amongst several others . [SEP]

[CLS] such receptors have been designed for a wide range of applications such as sensing , 2 removal of pollutants from solutions 3 and to transport anionic guests across biological membranes . [SEP]

[CLS] one large family of such receptors is based on metal B-material complexes with the ability to coordinate reversibly to the target anionic guest . [SEP]

[CLS] depending on the number and nature of the metal B-material ion B-material as well as its coordination environment , it is possible to tune the selectivity of metallo - receptors for a given oxoanion . [SEP]

[CLS] for example , di - zinc ( ii ) complexes have been shown to display high affinity for phosphate derivatives and , by tuning the coordination environment , display good selectivity for a given phosphate over other anions B-material . [SEP]

[CLS] one class of phosphate derivatives that attracted our attention are bisphosphonates such as etidronate and alendronate ( see scheme 1 ) . [SEP]

[CLS] these oxoanions act as inhibitors of osteoclastic bone resorption and are therefore used in the treatment of a variety of skeletal disorders such as paget´s disease and osteoporosis . [SEP]

[CLS] recent studies have also revealed that this type of bisphosphonates can induce apoptosis B-event in tumour cells B-material , are synergistic with antineoplastic drugs and can act as anti - angiogenic agents . [SEP]

[CLS] however , the use of bisphosphonates in the clinic has been limited since less than 1 % of an orally administered dose is taken up by the cell B-material . [SEP]

[CLS] this has been attributed to their negative electrostatic charge , which hinders their transport through the lipophilic B-property cell B-material membrane . [SEP]

[CLS] furthermore , bisphosphonates exhibit a short plasma half - life and are rapidly eliminated in urine . [SEP]

[CLS] to address these problems , liposomes B-nanoparticle , nanopeptides B-material , calcium B-material phosphate - dna nanoparticles B-nanoparticle and nanopolymers B-material have been explored as drug carriers . [SEP]

[CLS] with this in mind , the aim of the research herein presented was to study whether di - zinc ( ii ) complexes could act as good receptors for bisphosphonates and whether it would be possible to attach such host - guest systems to gold B-nanoparticle nanoparticles I-nanoparticle ( aunp B-nanoparticle ) as nanocarriers for future biological applications . [SEP]

[CLS] thus , we report the synthesis of the di - zinc ( ii ) molecular receptor B-material 2 ( see scheme 1 ) and its interactions with etidronate and alendronate . [SEP]

[CLS] the binding process has been studied by spectroscopic techniques ( i . e . uv - vis and 31 p nmr spectroscopy B-technique ) and the exact binding mode of both bisphosphonates to the receptor B-material has been established by x - ray crystallography . [SEP]

[CLS] furthermore , the drug - loaded metallo - receptor B-material was further functionalised with dithiocarbamate and successfully attached onto aunps B-nanoparticle ( see scheme 2 ) . [SEP]

[CLS] synthesis and spectroscopic characterization of di - zinc ( ii ) complex 2 . [SEP]

[CLS] the bis ( zinc ( ii ) dipicolylamine ) motif has been used extensively in receptors for several oxoanions such as phosphates and carboxylates B-material . [SEP]

[CLS] there is also one previous example where this type of complex has been incorporated into a receptor B-material for bisphosphonates . [SEP]

[CLS] therefore , we synthesised the di - zinc ( ii ) receptor B-material 2 ( see scheme 1 ) and explored its ability to selectively recognise alendronate and etidronate over several other anions B-material . [SEP]

[CLS] in addition to the di - zinc B-material recognition moiety , the complex also contains a benzylamine substituent since it can be readily converted into a dithiocarbamate which in turn would render the complex suitable for attachment to gold B-nanoparticle nanoparticles I-nanoparticle ( see below ) . [SEP]

[CLS] ligand 1 was obtained following a synthetic procedure previously reported for similar bisdipicolylamine compounds ( see scheme s1 ) . [SEP]

[CLS] metallo - receptor B-material 2 was synthesized by reacting 1 with two equivalents of zn ( oac ) 2 and one equivalent of nabf4 ( see scheme 1 ) . [SEP]

[CLS] 1 : synthetic route for the preparation di - zinc ( ii ) receptor B-material 2 and its complexes with bisphosphonate - based drugs ( i . e . etidronate and alendronate ) . [SEP]

[CLS] complex 3 is electrostatically neutral due to the protonation of the benzyl amine B-material group I-material while complex 4 is + 1 due to the protonation of both the benzylamine and the amine B-material of alendronate . [SEP]

[CLS] the 1 h and 13 c nmr spectrum of complex 2 ( as compared to 1 ) shows that the pyridine c / h are in two different chemical environments due to the coordination to the zinc ( ii ) centres ( see indicator B-property displacement assays ( ida ) and uv / vis titrations . [SEP]

[CLS] to study whether 2 could act as a molecular receptor B-material for bisphosphonate - based drugs , its interaction to etidronate and alendronate was investigated via ida . [SEP]

[CLS] the interaction of 2 with several other anions B-material which are physiologically relevant ( i . e . hp2o7 3 - , hpo4 2 - , so4 2 - , so3 2 - , co3 2 - , no3 - , oh - and cl - ) was also studied to establish its selectivity profile . [SEP]

[CLS] this was performed using pyrocatechol violet ( pv ) as an indicator B-property , which is yellow when free in solution but blue when coordinated to zinc ( ii ) . [SEP]

[CLS] compound 2 ( 50 µm ) was mixed with one molar equivalent of pv and the resulting 2 • pv complex was individually incubated B-technique with one molar equivalent of each anion B-material . [SEP]

[CLS] upon mixing with etidronate and alendronate , an instantaneous colour change was observed , indicating the displacement of the dye by the bisphosphonate drugs ( figure 1a ) . [SEP]

[CLS] in contrast , mixing 2 • pv with the other anions B-material under study did not generate a significant change in the colour of the original solution ( figure 1a ) . [SEP]

[CLS] the same experiment was repeated using 10 equivalents of each anion B-material ; in this case , besides etidronate and alendronate , pyrophosphate also induced a colour change ( consistent with previous reports showing that at high concentrations pyrophosphate binds to this type of di - zinc ( ii ) receptorssee figure s30 ) . [SEP]

[CLS] following this initial screening , the interaction between 2 • pv and the anions B-material was further analysed by uv - vis spectroscopy B-technique , which confirmed the ability of receptor B-material 2 to bind etidronate and alendronate with high selectivity over all other anions B-material investigatedexcept pyrophosphate which also shows some binding at high concentrations ( figure 1b ) . [SEP]

[CLS] quantitative determination of the binding affinity between receptor B-material 2 and the bisphosphonate drugs was assessed by uv - vis and 31 p nmr titrations ( figure 2 ) . [SEP]

[CLS] the uv - vis titration was performed by adding increasing amounts of either etidronate or alendronate to a solution of 2 • pv ( 50 µm ) . [SEP]

[CLS] the intensity of the uv - vis bands centred at 455 nm increases while the band centred around 650 nm decreases upon addition of the bisphosphonate anion B-material ( figure 2b ) . [SEP]

[CLS] from this data , the association constants for 2 with etidronate ( ka = 2 . 42±0 . 15 x 10 5 m - 1 ) and alendronate ( 2 . 25±0 . 16 x 10 5 m - 1 ) were calculated . [SEP]

[CLS] the interaction between 2 and the two drugs was also studied by p nmr spectroscopy B-technique in d2o at room temperature ( figure 2d ) . [SEP]

[CLS] upon addition of alendronate to a solution of 2 , a resonance at 21 . 9 ppm ( assigned to coordinated alendronate ) appeared and increased with subsequent additions of the anion B-material until ca . results were obtained for etidronate , figure s31 ) . [SEP]

[CLS] the uv - vis and 31 p nmr spectroscopic studies indicate that 2 binds to etidronate and alendronate in a 1 : 1 stoichiometry . [SEP]

[CLS] to confirm this , the method of continuous variation ( i . e . job ' s plots ) was applied ; as can be seen in figure 2c and s30c , these studies clearly show the presence of a 1 : 1 binding stoichiometry . [SEP]

[CLS] spectra of both these complexes in meod showed two doublets for the phosphorus B-material of the etidronate and alendronate in the range of 23 . 4 - 24 . 8and 21 . 9 - 22 . 9 ppm , respectively . [SEP]

[CLS] it is interesting to note that there are differences in the 31 p nmr spectra of 3 and 4 when recorded in d2o ( see figure 2d ) and meod ( see figures s10 and s12 ) . [SEP]

[CLS] in the former a single resonance is observed , while in meod two distinct doublets are observed , which is consistent with the two different phosphorous environments ( coupling to each other ) . [SEP]

[CLS] the formulation and purity of these host - guest complexes were confirmed by mass spectrometry and elemental analyses ( see experimental details ) . [SEP]

[CLS] single - crystal x - ray diffraction analysis . [SEP]

[CLS] the molecular structures of compounds 3 and 4 [SEP]

[CLS] were determined by single - crystal x - ray crystallography ( figures 3 and 4 functionalization of gold B-nanoparticle nanoparticles I-nanoparticle with receptors . [SEP]

[CLS] the next aim of this work was to explore the attachment of receptor B-material 2 ( loaded with bisphosphonates ) onto gold B-nanoparticle nanoparticles I-nanoparticle ( aunp B-nanoparticle ) to yield a potential drug delivery system . [SEP]

[CLS] as has been previously reported , dithiocarbamates are efficient groups for the attachment of small molecules onto gold B-nanoparticle nanoparticles I-nanoparticle . [SEP]

[CLS] thus , we functionalized the backbone of receptor B-material 2 with a dithiocarbamate to yield 5 as shown in scheme 2 . [SEP]

[CLS] 2 : synthetic route for the preparation of dithiocarbamate - modified di - zinc ( ii ) receptor B-material and the corresponding complexes with etidronate and alendronate . [SEP]

[CLS] subsequently , the modified receptor B-material 5 was loaded with either etidronate or alendronate to yield compounds 6 and 7 respectively . [SEP]

[CLS] due to the limited solubility B-property of 6 and 7 , it was not possible to obtain 1 h and c nmr spectra of good enough quality to assign all the resonances . [SEP]

[CLS] however , the 31 p nmr spectra in meod of these complexes showed the expected doublets for coordinated etidronate ( δ = 22 . 1 - 24 . 9 ppm ) and alendronate ( δ = 22 . 1 - 22 . 9 ppm ) . [SEP]

[CLS] in addition , esi ( + ) - ms showed the molecular ion B-material peaks for both the host - guest complexes : [ m + h ] + and [ m - bf4 ] + at 1079 . 70 and 1120 . 12 a . m . u . for 6 and 7 respectively . [SEP]

[CLS] these complexes were then attached to aunps B-nanoparticle which were also functionalised with thiolated oligonucleotides labelled with fluorescein ( fam - dna - sh ) to give the system greater biocompatibility B-property as well as a fluorescent B-property tag to help determining the dna loading on the aunp B-nanoparticle ( see below ) . [SEP]

[CLS] it is well established that passivation of aunps B-nanoparticle with a dense layer of oligonucleotides ( often referred to as ' spherical nucleic B-material acids I-material ' ) provides nanoconjugates with good solubility B-property profile , low cytotoxicity B-property and cell B-material permeability . [SEP]

[CLS] therefore , the following systems were prepared and studied ( see figure 5 ) : aunps B-nanoparticle without receptor B-material 2 or drug ( aunp B-nanoparticle - dnaas a control ) , with receptor B-material 2 but no drug ( aunp B-nanoparticle - dna - 5 ) , and with drug - loaded receptor B-material complexes 6 or 7 ( aunp B-nanoparticle - dna - 6 and aunp B-nanoparticle - dna - 7 ) . [SEP]

[CLS] the aunps B-nanoparticle were synthesized following previously reported procedures . [SEP]

[CLS] briefly , they were grown through the reduction of haucl4 with sodium B-material citrate and tannic acid to yield quasispherical , narrowly - dispersed aunps B-nanoparticle with an average core B-material diameter of 10 . 59 ± 1 . 8 nm . [SEP]

[CLS] the characterization of the aunps B-nanoparticle was carried out through uv - vis spectroscopy B-technique , dynamic B-technique light I-technique scattering I-technique ( dls ) , and transmission B-technique electron I-technique microscopy I-technique ( tem ) ( figure s32 and table s1 ) . [SEP]

[CLS] the changes observed in the hydrodynamic diameter ( dh ) and zeta B-property potential I-property ( ζ ) of the nps B-nanoparticle after functionalization ( see table s3 ) suggest that all three methods yield aunps B-nanoparticle passivated with both the oligonucleotides and receptor - drug conjugate 6 . [SEP]

[CLS] however , a higher oligonucleotide loadingwhich , in turn , increases the stability and biocompatibility B-property of the systemswas observed by adding the fam - dna - sh and receptor - drug complex together i . e . second method described above . [SEP]

[CLS] the oligonucleotide loading was estimated by treating the corresponding dna - passivated aunps B-nanoparticle with a large excess of mercaptoethanol following reported protocols . [SEP]

[CLS] incubation B-technique with mercaptoethanol displaces the fluorescently B-property - labelled oligonucleotides from the aunp B-nanoparticle surface , allowing the number of oligonucleotides attached per aunp B-nanoparticle to be calculated . [SEP]

[CLS] having established the best synthetic method , samples of aunp B-nanoparticle - dna - 5 and aunp B-nanoparticle - dna - 7 [SEP]

[CLS] ( in addition to aunp B-nanoparticle - dna - 6 as described above ) were prepared and fully characterised by s3 in the esi ) . [SEP]

[CLS] the largest difference is observed for aunp B-nanoparticle - dna - 7 ( with ζ = - 25 . 4 ± 1 . 6 cf . - 81 . 2 ± 0 . 9 for aunp B-nanoparticle - dna ) which can be attributed to alendronate ' s positively charged alkyl ammonium group . [SEP]

[CLS] additionally , there were changes in the uv - vis absorbance of the nanoparticles B-nanoparticle before and after functionalisation , which reflects the changes of optical properties of aunps B-nanoparticle caused by the coating B-material process ( figure 6a ) . [SEP]

[CLS] the tem images showed that the spherical morphology of the aunps B-nanoparticle is preserved after the formation of the aunp B-nanoparticle - dna - 6 and aunp B-nanoparticle - dna - 7 ( figure 6c and 6d ) . subsequently , the number of fam - dna molecules attached to the aunps B-nanoparticle was determined by fluorescence B-technique spectroscopy I-technique ( as described above using mercaptoethanol ) while the number of attached host - guest complexes was indirectly determined by quantifying the amount of zn via icp - ms ( see table 1 ) . [SEP]

[CLS] these measurements indicate that there are 69 and 79 molecules of etidronate and alendronate per aunp B-nanoparticle in aunp B-nanoparticle - dna - 6 and aunp B-nanoparticle - dna - 7 respectively . [SEP]

[CLS] interestingly , in the aunp B-nanoparticle - dna - 5 , aunp B-nanoparticle - dna - 6 and aunp B-nanoparticle - dna - 7 samples , a higher oligonucleotide loading was observed in comparison with aunp B-nanoparticle - dna sample . [SEP]

[CLS] this effect could be attributed to the stabilization of the negative charge of oligonucleotides strands by the presence of the complexes . [SEP]

[CLS] in summary , we have shown that di - zinc ( ii ) complex 2 binds bisphosphonates with high affinity and good selectivity over many other physiologically - relevant anions B-material . [SEP]

[CLS] the x - ray crystal structures of this receptor B-material bound to alendronate and etidronate show for the first time the exact binding mode of these oxoanions to a di - metallic receptor B-material . [SEP]

[CLS] we also show that by modifying the backbone of the receptor B-material , it is possible to load the drug - loaded receptor B-material onto aunps B-nanoparticle that have also been passivated with oligonucleotides to make them water B-property - soluble B-property and biocompatible B-property . [SEP]

[CLS] these new nanoconjugates are likely to be good vehicles B-material for the delivery of these drugs across the cell B-material membrane . [SEP]

[CLS] future work will explore this possibility . [SEP]

[CLS] general information . [SEP]

[CLS] 1 h nmr , c nmr and 31 p nmr spectra were recorded on either a bruker avance 400 mhz ultrashield nmr spectrometer or a bruker avance 500 mhz nmr spectrometer . [SEP]

[CLS] electrospray ionisation B-property mass spectra were obtained on a bruker daltonics esquire 3000 spectrometer . [SEP]

[CLS] the x - ray crystal structures where measured using an od xcalibur px ultra diffractometer ( 1 . 54184 a ) . [SEP]

[CLS] uv - vis spectra were collected with a perkin elmer uv - vis lambda 25 spectrophotometer . [SEP]

[CLS] fluorescence B-property measurements were made on a cary eclipse fluorescence B-property spectrophotometer . [SEP]

[CLS] hydrodynamic diameters and zeta B-property potentials I-property were measured on a malvern zetasizer nano zs instrument . [SEP]

[CLS] nanoparticles B-nanoparticle images were taken using a jeol jem - 2100 plus transmission electron microscope . [SEP]

[CLS] all reagents were purchased from commercial suppliers and used without further purification . [SEP]

[CLS] etidronate and alendronate were purchased as etidronate disodium hydrate and alendronate sodium B-material trihydrate , respectively . [SEP]

[CLS] the organic precursor d was prepared following a previously reported synthetic procedure ( scheme s1 ) . [SEP]

[CLS] for numbering of the 1 h nmr assignments shown below , please see the corresponding spectra in the esi . [SEP]

[CLS] to a solution of d ( 0 . 815 g , 1 . 45 mmol ) in methanol ( 20 ml ) benzaldehyde ( 0 . 177 ml , 1 . 74 mmol ) was added dropwise . [SEP]

[CLS] the reaction mixture was stirred for 2 h at room temperature . [SEP]

[CLS] nabh4 ( 110g , 2 . 90 mmol ) was then added to the reaction mixture and after stirring it for 4 h , the solvent was removed under vacuum and the excess nabh4 neutralised with saturated nh4cl aqueous solution ( 60 ml ) . [SEP]

[CLS] the product was extracted with dichloromethane and dried over na2so4 powder . [SEP]

[CLS] after filtration , the solvent was reduced under vacuum to yield a brown oil which was purified by silica column chromatography B-technique with chcl3 / meoh / et3n ( 94 : 5 : 1 ) as eluent to afford ligand 1 as a yellow oil . [SEP]

[CLS] yield : 87 % ( 0 . 819 g , 1 . 26 mmol ) . [SEP]

[CLS] s s1 - s4 for 1 h and c nmr spectra ; s5 - s8 for 2d nmr spectra ) . [SEP]

[CLS] in the c nmr [SEP]

[CLS] 1 : colorimetric response of 2 • pv to different anions B-material in 10 mm hepes solution at ph 7 . 4 at room temperature . [SEP]

[CLS] ( a ) with 1 eq of anions B-material . [SEP]

[CLS] ( b ) uv - vis spectra of 50 µm 2 • pv in 10 mm hepes solution at ph = 7 . 4 and 1 eq of anions B-material ( c ) uv - vis spectra of 50 µm 2 • pv in 10 mm hepes solution at ph = 7 . 4 and 1 eq . of etidronate , alendronate and 10 equivalents of common inorganic B-material anions I-material . [SEP]

[CLS] 2 : ( a ) indicator B-property displacement assay between 2 • pv and alendronate ; ( b ) uv spectra of 50 µm 2 • pv titrated with increasing amounts of 1 . 25 mm alendronate in 10 mm hepes solution , ph = 7 . 4 . [SEP]

[CLS] ( c ) job´s plot of 50 µm 2 • pv and alendronate in 10 mm hepes solution at ph = 7 . 4 . [SEP]

[CLS] ( d ) 31 p nmr ( 400 mhz , d2o ) spectra showed the titration of 2 with alendronate . [SEP]

[CLS] 1 association between the receptor B-material and bisphosphonates . [SEP]

[CLS] suitable crystals of compounds 3 and 4 were grown from acetone and methanol / toluene solutions respectively . [SEP]

[CLS] in both of these structures , the four negative charges of the bisphosphonate groups are delocalized between the four oxygen B-material atoms I-material coordinated to the zinc ( ii ) centres and the two remaining uncoordinated oxygen B-material atoms I-material . [SEP]

[CLS] this effect is evidenced in the relatively narrow distribution of the p - o distances , from 1 . 510 ( 2 ) a to 1 . 546 ( 3 ) a and 1 . 518 ( 3 ) a to 1 . 543 ( 3 ) a for 3 and 4 , respectively . [SEP]

[CLS] these values are intermediate B-property to the standard bond lengths reported for p - o ( 1 . 50 a ) and p = o ( 1 . 63 a ) . [SEP]

[CLS] the average values for the n - zn , odrug - zn and oligand - zn bond distances are 2 . 210 a , 2 . 063 a , 2 . 100 a for 3 , and 2 . 212 a , 2 . 059 a , 2 . 096 a for 4 . [SEP]

[CLS] in both structures the coordination geometry around the zinc ( ii ) centres corresponds to a distorted octahedron . [SEP]

[CLS] in 4 , the amine B-material group I-material of the coordinated alendronate is protonated giving an overall positive charge to the complex . [SEP]

[CLS] 3 . the crystal structure of 3 ( 50 % probability ellipsoids ) showing the interaction between the di - zinc ( ii ) receptor B-material and etidronate . [SEP]

[CLS] 4 . the structure of the cation B-material in the structure of 4 ( 50 % probability ellipsoids ) showing the interaction between the di - zinc ( ii ) receptor B-material and alendronate . [SEP]

[CLS] 5 : schematic representation of nanoconjugates aunp B-nanoparticle - dna - 6 and aunp B-nanoparticle - dna - 7 . [SEP]

[CLS] three different methods were studied to passivate the aunps B-nanoparticle with thiolated fluoresceinlabelled oligonucleotides and the receptor - drug 6 : ( i ) by first preparing aunp B-nanoparticle - dna and then adding 6 to the nanoparticles B-nanoparticle ; ( ii ) by adding fam - dna - sh and 6 at the same time to the unfunctionalized aunps B-nanoparticle ; ( iii ) by first adding 6 to the aunps B-nanoparticle and then the fam - dna - sh . [SEP]

[CLS] vis and fluorescence B-technique spectroscopy I-technique , dls , tem and inductively coupled plasma mass spectrometry ( icp - ms ) [SEP]

[CLS] the coating B-material of aunps B-nanoparticle with fam - dna - sh to yield aunp B-nanoparticle - dna induces a change dh from 21 . 4 ± 0 . 2 nm to 45 . 7 ± 0 . 4 nm , and a change ζ from - 34 . 8 ± 1 . 2 mv to - 81 . 2 ± 0 . 9 mv . [SEP]

[CLS] addition of the complexes ( 6 and 7 ) makes ζ less negative which is consistent with less dna being present on the surface of the aunps B-nanoparticle ( see table [SEP]

[CLS] 6 : ( a ) uv - vis spectra of aunps B-nanoparticle , aunp B-nanoparticle - dna , aunp B-nanoparticle - dna - 5 , aunp B-nanoparticle - dna - 6 and aunp B-nanoparticle - dna - 7 ; ( b ) size distribution of unfunctionalised aunps B-nanoparticle ; and tem of images of ( c ) aunp B-nanoparticle - dna - 6 and ( d ) aunp B-nanoparticle - dna - 7 . [SEP]

[CLS] in a 50 ml three - necked round - bottom flask under vigorous stirring [SEP]

[CLS] when the temperature reached 70 °c , haucl4 ( 0 . 41 ml , 10 mm ) was injected , resulting in a color change from colorless to pink . [SEP]

[CLS] stirring at 70 °c for a further 10 minutes generated a solution of seed of the solution and replacing with sodium B-material citrate ( 9 . 1 ml , 2 . 2 mm ) . [SEP]

[CLS] when the temperature reached 70 °c again , two injections of haucl4 ( 0 . 2 ml , 10 mm ) on a time interval of 10 minutes were done . [SEP]

[CLS] this growing process ( sample dilution followed by the injection of haucl4 ) was followed by uv - vis spectroscopy B-technique and was repeated until the nanoparticles B-nanoparticle reached the desired size . [SEP]

[CLS] functionalization of gold B-nanoparticle nanoparticles I-nanoparticle . [SEP]

[CLS] au nps B-nanoparticle were functionalized with fam - dna - sh and the corresponding complexes ( i . e . 5 , 6 or 7 ) based on general methodologies previously described in the literature . fam - tt - ggg - tta - ggg - tta - ggg - tta - ggg - tt - ( ch2 ) 6 - sh ( fam - dna - sh ) oligonucleotide was selected with a thiol B-material modifier on the 3 ' end and a fluorescein ( as an optical label ) amidite group on the 5 ' end . [SEP]

[CLS] before use , tris ( 2 - carboxyethyl ) phosphine ) ( tcep ) was added to fam - dna - sh in a 100x excess and the mixture was shaken for 1 hr at room temperature . [SEP]

[CLS] final concentrations of tcep and fam - dna - sh were 5 mm and 50 μm respectively . [SEP]

[CLS] 1 wt % tween 20 ( 68 . 7 μl ) was added to the aunps B-nanoparticle ( 12 . 1 nm , 6 . 87 ml ) and the mixture was stirred for 1 min . [SEP]

[CLS] fam - dna - sh ( 50 μm ) and the corresponding bimetallic zinc B-material complex ( 500 μm ) was added at a volume that allowed for 90 and 350 oligonucleotide strands and complex per aunp B-nanoparticle . [SEP]

[CLS] nacl ( 5 m ) was then added until its final concentration in the mixture reached 800 mm . the solution was incubated B-technique for 1 h at 25 °c with gentle agitation and then centrifuged at 30 , 000 rpm for 15 min at 15 °c . [SEP]

[CLS] the supernatant was removed and the nps B-nanoparticle were redispersed in milli - q water B-material . [SEP]

[CLS] this centrifugation process was repeated at least 3 times to ensure thorough washing of the aunps B-nanoparticle . [SEP]

[CLS] wr2 ( all ) = 0 . 1796 , 8585 independent observed absorption - corrected reflections [ | fo | > 4σ ( | fo | ) , completeness to θfull ( 67 . 7° ) = 98 . 4 % ] , 757 parameters . [SEP]

[CLS] ccdc 1984671 . [SEP]

[CLS] see esi for further discussion about this x - ray crystal structure . [SEP]

[CLS] samples [SEP]

[CLS] all samples were freshly prepared in 10 mm hepes buffer ( ph 7 . 1 ) prior to measurements . [SEP]

[CLS] all measurements were repeated 3 times . [SEP]

[CLS] for optical tests , 1 ml of 2 • pv ( 50 μm ) was mixed with 5 μl ( 1 eq . ) or 50 μl ( 10 eq . ) of the corresponding anion B-material ( 10 mm ) in 10 mm hepes solution at ph 7 . 4 at room temperature . [SEP]

[CLS] the mixture was stirred gently and then left to stand for 10 min . [SEP]

[CLS] to obtain the uv - vis spectra , 700 µl 2 • pv were added to a uv - vis cuvette and mixed with one or ten molar equivalent of each anion B-material under study in a buffer solution ( 10 mm hepes at ph = 7 . 4 ) at room temperature . [SEP]

[CLS] aunps B-nanoparticle of different sizes were synthesized following protocols reported from puntes et al . [SEP]

[CLS] sodium B-material citrate ( 25 ml , 2 . 2 mm ) , tannic acid ( 17 µl , 2 . 5 mm ) and potassium B-material carbonate B-material ( 170 µl , 150 mm ) was heated [SEP]

[CLS] the field of structural dna nanotechnology applies the programmability of watson - crick base pairing to the construction of custom nanostructures that are prescribed by the sequence information encoded in dna molecules . [SEP]

[CLS] precisely defined geometries , highly programmable molecular interactions , and outstanding biocompatibility B-property make dna nanostructures a new category of nanocarriers for drug delivery . [SEP]

[CLS] over the past decade , the potential of using dna nanocarrier - based formulation for cancer therapy has been extensively explored with the successful implementation of various therapeutic strategies , both in vitro and in vivo . [SEP]

[CLS] moreover , dna nanocarriers can be encoded with complex instructions via sequence design , enabling therapeutic functions to be executed in a programmed , automatic manner . [SEP]

[CLS] in this review , we summarize recent advances and discuss the challenges and opportunities in designer dna nanostructure - enabled therapeutics . [SEP]

[CLS] nanotechnology is an interdisciplinary research field focusing on the manipulation and organization of matter at the nanometer scale with the aim of achieving novel functions . [SEP]

[CLS] in particular , nanomedicine , a branch of nanotechnology , takes advantage of the unique properties of nanomaterials B-material for diagnostics and therapeutics . [SEP]

[CLS] it has been proven that including nanocarriers in therapeutic formulations can improve effectiveness and minimize adverse effects of conventional drugs . [SEP]

[CLS] by 2016 , over 50 nanomedicines had been approved by the u . s . food and drug administration ( fda ) , with many more undergoing clinical trials . [SEP]

[CLS] a majority of fda - approved nanomedicines are based on micellar , liposomal B-nanoparticle , polymeric , and inorganic B-nanoparticle nanoparticles I-nanoparticle . [SEP]

[CLS] they are more or less limited by the heterogeneity in size and shape , chemical or physical instability , and potential cytotoxicity B-property . [SEP]

[CLS] research on molecular self - assembly has suggested the prospects of using a programmable biopolymeric B-material material B-material , dna , to enrich the choices of nanocarriers . [SEP]

[CLS] although at an early stage of development , the use of dna nanocarriers to facilitate drug delivery has demonstrated profound potential ( figure 1 ) . [SEP]

[CLS] dna is the most widely used molecular building block for nanofabrication via self - assembly . [SEP]

[CLS] besides its biocompatible B-property nature , dna possesses several uniquely advantageous characteristics , such as a well - defined geometry , predictable and programmable complementarity , abundant choices of sequences , thermostability , affordable synthesis chemistry , and readily accessible chemical and enzymatic tools for modification . [SEP]

[CLS] the history of using dna as a nanoscale building material B-material can be traced back to 1982 when ned seeman proposed the concept that ' ' migrationally immobile junctions ' ' could be assembled from rationally designed sequences and further joined together to form two - dimensional ( 2d ) or three - dimensional ( 3d ) networks through complementary single - stranded overhangs called sticky ends ( figure 2a ) . [SEP]

[CLS] the early work in structural [SEP]

[CLS] the bigger picture [SEP]

[CLS] the development of nanomedicine is closely related to the evolution of nanocarriers that endow therapeutic agents with improved efficacy , safety , and targeting specificity . [SEP]

[CLS] a grand challenge in nanomedicine is the ability to design suitable nanocarriers that can precisely transport therapeutic agents across biological barriers B-property in the complex environment of living organisms . [SEP]

[CLS] the programmable and biocompatible B-property nature of dna has enabled the rational design of tailored dna nanocarriers for targeted drug delivery , which has greatly contributed to the remarkable progress in cancer therapy . [SEP]

[CLS] additionally , dna nanotechnology - enabled therapeutic systems have demonstrated profound potential in the development of smart therapeutic robotic systems and the treatment of renal diseases . [SEP]

[CLS] in this review , we discuss the roles of dna nanostructures in different therapeutic strategies and highlight model systems that hold promise for clinical translation in the long term . [SEP]

[CLS] random dna tilings with programmable disorder a structural foundation of dna nanotechnology therapeutic applications of dna nanotechnology b ned seeman proposed the concept that " migrationally immobile junctions " could be assembled from dna oligonucleotides with rationally designed sequences and further linked into networks assembly of an immobile holliday junction from four synthetic dna oligonucleotides folate - mediated cellular uptake of dna nanotubes B-nanoparticle delivery of dna tetrahedra into mammalian cells B-material without the aid of transfection reagents gigadalton 3d polyhedra 3d molecular canvas assembled from 10 , 000 unique ssts 51 sustained delivery of dox and cpg motifs in vivo by dna hydrogels dna nanotechnology focused on exploring design principles and assembly methods for building complex structures ( figure 1a ) . [SEP]

[CLS] after more than 30 years of development , the structural complexity of dna architectures has reached an unprecedented level . [SEP]

[CLS] research on the fundamental aspects of dna - based self - assembly has facilitated the rational design of custom dna nanostructures that can be tailored for specific purposes . [SEP]

[CLS] in the past decade , numerous attempts have been made by dna nanoscientists to use the dna - nanotechnology - based platform for therapeutic applications ( figure 1b ) . [SEP]

[CLS] dna nanostructures are primarily used as carriers to deliver therapeutic agents , including anticancer B-property drugs , antisense oligonucleotides ( asos ) , photosensitizers B-property , nanoparticles B-nanoparticle , and proteins B-material , to pathogenic sites . moreover , other functional modules can be feasibly integrated into dna - based nanocarriers , allowing for real - time tracking , precise targeting , conditional activation , and controlled release . [SEP]

[CLS] the versatility of dna nanostructures enables the implementation of different therapeutic strategies , including chemotherapy , gene therapy , phototherapy , and immunotherapy , both in vitro and in vivo . [SEP]

[CLS] additionally , the dna - nanotechnology - based therapeutic platform provides new solutions to multidrug resistance ( mdr ) , tumor B-material vascularization , and acute kidney injury . [SEP]

[CLS] the successful proof - of - concept applications in therapeutics have inspired ever - increasing efforts for ' ' bench - to - bedside ' ' translation . [SEP]

[CLS] in this review , we first introduce the fundamental design strategies and principles that have transformed the field of structural dna nanotechnology . [SEP]

[CLS] criteria for developing dna - based nanocarriers are then discussed in terms of stability , cellular uptake , targeting specificity , and economical manufacturing . [SEP]

[CLS] in addition , recent advances in the therapeutic applications of dna nanostructures are categorized and summarized based on their therapeutic strategies , including chemotherapy , gene therapy , phototherapy , immunotherapy , combination therapy , and therapeutic dna nanorobots . [SEP]

[CLS] as a case study , we discuss the potential use of dna nanostructures for the treatment of kidney diseases . [SEP]

[CLS] at last , we further discuss the challenges and potential future directions for the therapeutic applications of structural dna nanotechnology . [SEP]

[CLS] structural dna nanotechnology exploits the hybridization of complementary dna sequences to create structures via the self - assembly of dna building blocks . [SEP]

[CLS] a core B-material aim of structural dna nanotechnology is to use dna nanostructures for the organization of other molecules and materials with nanometer precision in order to engineer novel functions . [SEP]

[CLS] to this end , structural dna nanotechnology initially focused on the exploration of structural motifs that could be rationally designed , which laid the foundation for the rapid evolution of the field since 2000s . [SEP]

[CLS] in this section , we provide a brief overview regarding the fundamental design strategies and principles of structural dna nanotechnology . [SEP]

[CLS] comprehensive reviews can be found elsewhere in the literature . [SEP]

[CLS] design strategies seeman ' s original concept of ' ' migrationally immobile junctions ' ' was validated soon after it was proposed through the assembly of an immobile holliday junction from four synthetic dna oligonucleotides with rationally designed sequences and prescribed complementarity . [SEP]

[CLS] based on branched junctions , various covalently closed , discrete 3d objects , such as a cube and tetrahedra , were constructed ( figure 2b ) . [SEP]

[CLS] later on , modular dna tiles were proposed as nanoscale building blocks to construct extended , higher - order structures , including discrete nanocages B-nanoparticle , nanotubes B-nanoparticle , 27 2d arrays , and macroscopic crystals , via sticky end interactions ( figure 2c ) . [SEP]

[CLS] the groundbreaking technique of scaffolded dna origami was developed by folding a long single - stranded dna ( called a scaffold ) , typically derived from m13mp18 bacteriophage , into target shapes with the help of hundreds of auxiliary ' ' staple strands ' ' ( figure 2d ) . [SEP]

[CLS] as an extension of this concept , 3d origami structures were designed by packing dna helices into various 3d lattices . [SEP]

[CLS] via targeted insertions and deletions of base pairs , as well as curved - surface rendering , dna origami with complex curvatures can be reliably created . [SEP]

[CLS] in the dna origami design , each staple strand is uniquely addressable , which means it has a unique sequence and occupies a unique position that can be addressed as a ' ' pixel ' ' on the design , making dna origami a versatile platform to organize other molecules with nanometer precision by placing them on these ' ' pixels . [SEP]

[CLS] ' ' new strategies have further simplified the design of complex dna nanostructures . [SEP]

[CLS] single - stranded tile ( sst ) is the simplest form that a tile can take , as it is only composed of concatenated sticky ends . [SEP]

[CLS] complex structures , including 2d patterns , discrete 3d objects , and crystals , can be constructed by sculpting or packing the molecular canvas formed by a large number of unique ssts ( figure 2e ) . [SEP]

[CLS] methods for designing wireframe dna origami with either single - helix or reproduced with permission from seeman . copyright 1982 elsevier . [SEP]

[CLS] ( b ) discrete nanoobjects can be assembled from oligonucleotides with rationally designed sequences and complementarities . [SEP]

[CLS] a ~ 7 nm dna cube is the earliest polyhedral object constructed from dna . [SEP]

[CLS] ( c ) dna tile - based self - assembly is a feasible approach to create higher - order structures from modular building blocks . [SEP]

[CLS] for example , a 4 - by - 4 dna tile can be assembled from several oligonucleotides and further linked into 2d lattices through complementary sticky ends . [SEP]

[CLS] ( d ) dna origami is the folding of a long , single - stranded dna ( termed ' ' scaffold ' ' ) into 2d or 3d shapes with the help of hundreds of short dna oligonucleotides ( termed ' ' staples ' ' ) . [SEP]

[CLS] ( top right ) reproduced with permission from rothemund . [SEP]

[CLS] copyright 2006 springer nature . [SEP]

[CLS] ( bottom right ) reproduced with permission from castro et al . copyright 2011 springer nature . [SEP]

[CLS] ( e ) single - stranded tiles ( ssts ) can be programmed to assemble into 2d or 3d shapes without the guidance of a scaffold . [SEP]

[CLS] ssts interact with each other through complementary domains , in a way analogous to ' ' lego ' ' bricks . [SEP]

[CLS] ( top right ) reproduced with permission from wei et al . copyright 2012 springer nature . [SEP]

[CLS] ( bottom right ) reproduced with permission from ke et al . copyright 2012 aaas . [SEP]

[CLS] ( f ) single - stranded dna origami is the unimolecular folding of a long single - stranded dna into nanostructures through paranemic cohesions . [SEP]

[CLS] reproduced with permission from han et al . copyright 2017 aaas . [SEP]

[CLS] review double - helix edges offer new possibilities for developing dna frameworks . the design of single - stranded dna origami further enables a unimolecular folding of a single - stranded dna of over several kilobases into discrete structures ( figure 2f ) . [SEP]

[CLS] the size and complexity of dna assemblies are further advanced by a series of scaling - up strategies . [SEP]

[CLS] 2d random tilings , 3d polyhedra , dynamic devices , and gigadalton - scale objects can be built with high quality by assembling individual dna origami into extended structures . [SEP]

[CLS] through a ' ' fractal assembly ' ' strategy , micron - scale , fully addressable arrays that displayed user - defined patterns were made from the hierarchical , multistage assembly of up to 64 unique components . [SEP]

[CLS] in the sst system , the molecular canvas assembled from ssts was further expanded to up to 30 , 000 unique components . [SEP]

[CLS] feasible methods for fabricating micronsized dna assemblies from a large number of unique building units will enable the development of molecular devices with sizes comparable with cellular organelles and provide the platform for various applications including biomimetics and therapeutics . [SEP]

[CLS] in addition , dna - based nanomaterials B-material such as hydrogels and noncanonical nanoflowers have also been applied to biomedical applications and are discussed in this review . [SEP]

[CLS] spherical nucleic B-material acids I-material ( snas ) , including dna - functionalized inorganic B-nanoparticle nanoparticles I-nanoparticle , polymersomes , micelles B-material , and liposomes B-nanoparticle , are distinct from the abovementioned dna nanostructures , as they are the covalent coating B-material of a core B-material material B-material with a layer of highly oriented oligonucleotides . [SEP]

[CLS] these groups of dna - functionalized materials and their derivatives have been extensively researched and comprehensively reviewed elsewhere in the literature and are not covered in this review . [SEP]

[CLS] no matter how complicated the dna structure is , the physiochemical principle it follows is the maximization of base - pairing events ( i . e . , reducing the thermodynamic free energy of the whole self - assembly system ) . [SEP]

[CLS] second , complex , higher - order structures can be produced from modular , branched building blocks . [SEP]

[CLS] moreover , given the noncovalent , reversible nature of dna hybridization , choosing proper conditions could guide the self - assembly pathway to favor the rapid production of desired nanostructures with high yield . [SEP]

[CLS] finally , dynamic properties such as reconfiguration , unidirectional motion , and reversible assembly can be integrated into structures via an enzyme - free strand displacement mechanism . [SEP]

[CLS] overall , structural dna nanotechnology offers tremendous design space for nanofabrication , setting the groundwork for diverse applications . [SEP]

[CLS] an ideal drug - delivery system improves drug efficacy and safety by fine - tuning its retention and specificity in vivo . [SEP]

[CLS] as a crucial component , the carrier for drug delivery should fulfill the following criteria : ( 1 ) it should be chemically inert and biologically stable in physiological environments ; ( 2 ) be nontoxic , nonimmunogenic , and compatible with living organisms ; ( 3 ) must have a controllable retention time and a clear clearance pathway ; ( 4 ) should function specifically at the pathogenic site and have minimal effect on healthy tissues ; and ( 5 ) be scalable and cost efficient . [SEP]

[CLS] synthetic dna nanostructures do not inherently meet all the criteria , but they can be modified to better fulfill them . [SEP]

[CLS] moreover , the programmability of dna - based platform is not found in any other systems , making it one of the most promising candidates for therapeutics . [SEP]

[CLS] in this section , we discuss prior works on quantifying and improving characteristics of dna nanostructures with respect to the abovementioned criteria . [SEP]

[CLS] stability under physiological conditions dna nanostructures are usually prepared in buffers containing approximately 10 mm mg 2 + or 1 . 0 m na + , since cations B-material can reduce charge repulsion between closely packed dna helices , keeping structures from denaturation . [SEP]

[CLS] well - formed dna origami can withstand repeated freezing and thawing cycles in buffer containing sufficient mg 2 + and cryoprotectants , facilitating long - term cryopreservation . [SEP]

[CLS] however , most dna nanostructures are susceptible to low cation B-material concentration and nuclease digestion in physiological environments . [SEP]

[CLS] the tolerance of dna nanostructures to cation B-material depletion and nuclease digestion is design dependent . [SEP]

[CLS] in general , less compact structures can better withstand lower cation B-material concentrations , while more compact structures are more resistant to nuclease digestion . [SEP]

[CLS] for example , in contrast to a 24 - helix bundle with a denser packing of dna helices , a 6 - helix bundle can be assembled in buffers containing less cations B-material and remain intact under low - mg 2 + conditions . [SEP]

[CLS] wireframe origami can even be folded in mg 2 + - free buffers commonly used in biomedical research , such as phosphate - buffered saline ( pbs ) . [SEP]

[CLS] compared with duplex dna or double - crossover tiles , paranemic crossover ( px ) tiles with a higher number of crossovers showed enhanced nuclease resistance . [SEP]

[CLS] this effect can be attributed to local steric hindrance and global conformational strain and is in agreement with real - time visualization and computational modeling of dna origami digestion by nucleases . [SEP]

[CLS] taken together , these examples suggest the possibility of tuning the stability of dna nanostructures by rational design . [SEP]

[CLS] to maintain structural integrity under physiological conditions , it is necessary to protect dna nanostructures against cation B-material depletion and nuclease digestion with proper modifications ( figure 3a ) . [SEP]

[CLS] synthetic oligonucleotides with unnatural backbone , base , or left - handed chirality are suitable building units for assembling discrete or periodic nanostructures with improved serum stability . [SEP]

[CLS] however , their usage in stabilizing complex dna nanostructures is usually hindered by the high synthesis cost . [SEP]

[CLS] chemical or enzymatic ligation of nick points and photocross - linking of thymine bases 69 make individual components topologically interlocked for a better resistance against cation B-material depletion and nuclease digestion . [SEP]

[CLS] decorating or coating B-material dna nanostructures with hexaethylene glycol ( heg ) , lipid B-material bilayer I-material , dendritic oligonucleotides , peptoids , peptides B-material , albumins , and cationic B-material block co - polymers B-material based on oligolysine - polyethylene glycol ( peg ) , poly ( 2 - ( dimethylamino ) ethyl methacrylate ) , chitosan B-material , and linear polyethylenimine ( lpei ) helps shield them from nuclease digestion , greatly extending their half - life in cell B-material - culture media ( typically supplemented with 10 % fetal bovine serum ) or in vivo . [SEP]

[CLS] unlike dna nanostructures , dna - based nanoparticles B-nanoparticle ( e . g . , nanoflowers ) acquire nuclease resistance via a dense dna packaging . [SEP]

[CLS] notably , single - stranded dna origami has extraordinary thermostability , as it is analogous to a fully ligated dna structure . [SEP]

[CLS] its potential use as a drug carrier remains to be explored . [SEP]

[CLS] despite the charge repulsion between dna nanostructures and the cellular membrane , various dna nanostructures can be readily internalized into mammalian cells B-material via endocytosis B-event . [SEP]

[CLS] cell B-material type and the properties of dna nanostructures such as size , shape , and surface chemistry are the major factors that determine the route of endocytosis B-event . [SEP]

[CLS] general trends derived from other materials can hardly be adapted to dnabased systems due to the distinct surface chemistry . [SEP]

[CLS] dna nanostructures might be internalized into mammalian cells B-material through multiple pathways , given that their sizes range from a few nanometers to the submicron scale ( figure 3b ) . [SEP]

[CLS] a selection of recent studies focusing on the pathways of cellular uptake is discussed here . [SEP]

[CLS] comprehensive reviews on the cellular delivery of dna nanostructures can be found elsewhere in the literature . [SEP]

[CLS] a dna tetrahedron was one of the earliest structures proven to enter mammalian cells B-material without the aid of transfection reagents . [SEP]

[CLS] internalized tetrahedra were found unmodified dna nanostructures are usually susceptible to cation B-material depletion and enzyme digestion due to the charge repulsion between negatively charged dna backbones and the existence of nick points between individual strands . [SEP]

[CLS] ligation of nick points , cross - linking , and surface coating B-material are widely used strategies for protecting dna nanostructures from denaturation or degradation under physiological conditions . [SEP]

[CLS] ( b ) illustration depicting the cellular uptake pathways of dna nanostructures . [SEP]

[CLS] a dna tetrahedron ( 7 nm ) and a dna origami rod ( 127 nm in length ) are both internalized into hela cells B-material via caveolaemediated endocytosis B-event . [SEP]

[CLS] a dna nanoribbon with a high aspect ratio takes the clathrin - mediated endocytic pathway into h460 cells B-material . [SEP]

[CLS] the disulfide - modified dna nanospheres B-nanoparticle are directly internalized into the cytosol of hela cells B-material through a nonendocytic pathway . [SEP]

[CLS] ( c ) a variety of targeting modules , including aptamer , antibody B-material , small - molecule ligand , peptide B-material , and protein B-material , have been integrated onto dna - based carriers , resulting in improved targeting specificity and cellular uptake efficiency . [SEP]

[CLS] localized in the cytoplasm and also substantially intact . [SEP]

[CLS] as further elucidated by single - particle tracking , caveolin - dependent endocytosis B-event , followed by microtubuledependent transportation to the lysosomes , was identified as the primary uptake and intracellular trafficking mechanism in hela cells B-material . [SEP]

[CLS] the underlying physical mechanism was obtained through a coarse - grained modeling of the tetrahedron - cell B-material membrane interaction . [SEP]

[CLS] the modeling results suggested that tetrahedra predominantly attacked the spots of slight or no charge repulsion on the semifluidic membrane with their corners . [SEP]

[CLS] dna origami can be folded into arbitrary shapes , facilitating a systematic evaluation of the effect of size and shape on endocytosis B-event . [SEP]

[CLS] screening the shape - dependent uptake in three cell B-material lines representing endothelial , epithelial , and immune cells B-material uncovered a general trend wherein larger origami with more compact helical arrangement could be more efficiently internalized than smaller , less compact ones . [SEP]

[CLS] a similar trend was observed in lung cancer cell B-material lines : larger origami were more preferred than smaller ones ; compact , rod - shaped origami were more efficiently internalized than branched , tetrahedron - shaped ones . [SEP]

[CLS] the detailed cell B-material - internalization process of the large rod was visualized in the latter study , which was mediated by scavenger receptors and was likely to follow a caveolin - dependent pathway to late endosomes and lysosomes . [SEP]

[CLS] this result is consistent with the co - localization of tubular origami and lysosomes in nih 3t3 cells B-material observed by super - resolution fluorescence B-technique microscopy I-technique . [SEP]

[CLS] dna assemblies can also be internalized via clathrin - mediated or nonendocytic pathways [SEP]

[CLS] however , not many different shapes have been tested for their internalization pathways . [SEP]

[CLS] moreover , cellular uptake is usually quantified by fluorescence - based techniques , which can be affected by a number of factors , including degradation of dna structures , cellular uptake of fluorophores , and local environmental changes . [SEP]

[CLS] given the fact that cell B-material types differ vastly regarding their uptake efficiency , there are no comprehensive rules to predict the entry , biodistribution , and fate of dna nanostructures . [SEP]

[CLS] further research is necessary to unravel the complex mechanisms of cellular uptake and to seek non - endo / lysosomal pathways to circumvent the acidic environment in the lysosome for the efficient delivery of therapeutic agents . [SEP]

[CLS] studies on the in vivo distribution of dna nanostructures in healthy mice suggest the preferential accumulation in liver or kidney after intravenous injection into the blood circulatory system . [SEP]

[CLS] then , dna nanostructures are degraded or excreted within 24 h . [SEP]

[CLS] encapsulating dna nanostructures with pegylated lipid B-material bilayers I-material can help retain over 80 % of the administered dose throughout the mice as visualized 2 h after the initial injection . [SEP]

[CLS] topical medication is another potential solution to circumvent rapid clearance in systemic administration . [SEP]

[CLS] transdermal drug delivery is especially suitable for skin cancer treatment and has been applied to the mouse melanoma model with initial success . [SEP]

[CLS] dna nanostructures interact with cells B-material primarily through receptors displayed on the cellular membrane . [SEP]

[CLS] specific targeting and enhanced cellular uptake can be achieved by tagging dna nanostructures with ligands that can be recognized by the receptors ( figure 3c ) . [SEP]

[CLS] for example , folate modification enabled the specific internalization of dna nanotubes B-nanoparticle into kb cells B-material . [SEP]

[CLS] enhanced cellular uptake of a rectangular dna origami by hek293 cells B-material was facilitated by virus - capsid protein B-material coating B-material . [SEP]

[CLS] in addition , dna aptamers that are selected via cell - selex ( systematic evolution of ligands by exponential enrichment ) are widely used as targeting modules , as they can be incorporated into most dna nanocarriers . furthermore , the cell B-material entry and transport pathways of dna nanocarriers can be readily modulated by varying the targeting molecules . [SEP]

[CLS] the endocytic pathway usually determines the destination of intracellular transport . [SEP]

[CLS] most dna nanostructures and their cargo are ultimately transported to lysosomes for degradation . [SEP]

[CLS] thus , endolysosomal escape is necessary so that dna nanostructures can circumvent the acidic interior of lysosomes . [SEP]

[CLS] dna nanostructures can be modified with a secondary transport signal in order to be re - directed to target other organelles . [SEP]

[CLS] for example , signaling peptides B-material were anchored onto a dna tetrahedron to facilitate nucleus targeting . [SEP]

[CLS] modifying dna nanostructures to take nonendocytic or endosomal escape pathways is a key strategy for targeting specific organelles which remains to be explored . [SEP]

[CLS] high synthesis cost and long reaction time are two obstacles that hinder the rapid production of complex dna nanostructures in large quantities . [SEP]

[CLS] biotechnological mass - production methods based on enzymatic amplification or bacteriophage replication have facilitated large - scale synthesis of replicable dna nanostructures , and single - stranded dna that can be used as the scaffolds or staples for assembling dna origami . [SEP]

[CLS] remarkably , by including selfexcising dnazyme sequences in the single - stranded precursor dna produced by bacteriophages , target dna can be produced without the need for costly restriction endonucleases . [SEP]

[CLS] the production cost of folded origami is estimated to be $ 25 per milligram for a liter - scale lab setup and even lower for a pilot - scale setup . [SEP]

[CLS] as a highly cooperative process , the folding of a dna origami can be completed at a constant temperature within minutes . [SEP]

[CLS] taking advantage of this characteristic , rapid and scalable self - assembly of dna origami can be carried out with widely available lab equipments . [SEP]

[CLS] moreover , scalable methods for scaffold purification by selective polymer B-material catch and release and for origami purification by rate - zonal centrifugation and peg - induced precipitation further reduced the cost of preparing pure dna nanostructures . [SEP]

[CLS] methods for economical and scalable synthesis , fabrication , and purification will benefit applications that require dna nanostructures in large quantities and high purities , including therapeutics . [SEP]

[CLS] with a better understanding of their behaviors under physiological conditions and interactions with cells B-material , dna nanostructures have been extensively explored as a multifunctional platform to deliver therapeutic agents for the implementation of various in vitro and in vivo cancer - therapeutic strategies . [SEP]

[CLS] in this section , we summarize these strategies and highlight those successful examples demonstrated in vivo . [SEP]

[CLS] as the most widely used strategy for cancer treatment , chemotherapy is conducted by delivering cytotoxic B-property therapeutic agents to their functional sites . [SEP]

[CLS] dna - based drug - delivery systems use dna nanostructures or dna - based nanoparticles B-nanoparticle as carriers to improve the biodistribution , specificity , and efficacy of conventional drugs . [SEP]

[CLS] the safety concerns on using dna nanostructures can be precluded with appropriate design of dna sequences ( e . g . , obviating the use of functional dna modules like as1411 , a 26 - base guanine - rich dna aptamer with potential apoptotic induction activity ) . [SEP]

[CLS] to date , many dna - based carriers have been proven to have little cytotoxicity B-property and are primarily used as the hub to integrate drug loading , targeting , and release modules together . [SEP]

[CLS] doxorubicin B-material ( dox ) is widely used as a model drug as it can be easily loaded onto double - stranded dna B-event by I-event intercalation I-event and released by disrupting the dna duplex . [SEP]

[CLS] daunorubicin is another intercalating drug that has been delivered in a similar way . [SEP]

[CLS] other common model drugs , such as floxuridine ( fu ) , paclitaxel B-material ( ptx ) and camptothecin ( cpt ) , are usually loaded onto the dna carriers by conjugation or encapsulation . [SEP]

[CLS] some dna nanostructures , such as tetrahedra and origami , have the intrinsic ability to transport drug molecules into cancerous cells B-material without the aid of transfection reagents . [SEP]

[CLS] the loading B-property efficiency I-property and release kinetics of intercalating drugs can be modulated by designing dna origami carriers with different degrees of global twist ( figure 4a ) . [SEP]

[CLS] notably , dna origami can enhance the cellular uptake and distribution of dox and daunorubicin in dox - resistant breast adenocarcinoma ( mcf - 7 ) cells B-material and daunorubicin - resistant leukemia ( hl - 60 / adr ) cells B-material , respectively , resulting in a higher cytotoxicity B-property than free drug at equal concentrations . [SEP]

[CLS] targeted chemotherapy was facilitated by targeting molecule - functionalized dna nanocarriers ranging from aptamer - drug conjugates , nanoflowers , to dna nanostructures ( figure 4b ) . [SEP]

[CLS] moreover , drug release can be triggered by the degradation of carriers into nontoxic molecular components in response to a series of molecular stimuli or cancer hallmarks . [SEP]

[CLS] successful demonstration of improved specificity and efficacy in vitro lays the groundwork for transferring dna - based drug delivery systems toward in vivo implementation . [SEP]

[CLS] the efficacy of several dna - based chemotherapeutic systems has been proven in mouse models . [SEP]

[CLS] an aptamer - tethered dna duplex chain ( termed ' ' nanotrain ' ' ) was self - assembled via hybridization chain reaction ( hcr ) , which specifically delivered dox to human t cell acute lymphocytic leukemia ( cem ) cells and slowed down tumor B-material growth in a mouse xenograft model . [SEP]

[CLS] due to a wide distribution in size , drugs delivered by this type of carriers are not homogeneous ; i . e . , each carrier dox can be easily loaded onto dna nanostructures by intercalating between base pairs . [SEP]

[CLS] twisted dna origami nanotubes B-nanoparticle with 12 bp / turn showed a higher loading capacity and a more sustained release , compared to straight ones with 10 . 5 bp / turn . [SEP]

[CLS] reproduced with permission from zhao et al . copyright 2012 american chemical society . ( b ) muc1 aptamer - modified dna icosahedra for targeted delivery of dox into mcf - 7 cells B-material . [SEP]

[CLS] reproduced with permission from chang et al . copyright 2011 american chemical society . [SEP]

[CLS] ( c ) dna origami for dox delivery in vivo . [SEP]

[CLS] dox - loaded dna origami showed passive tumor B-material accumulation and antitumor efficacy without observable systemic toxicity B-property . reproduced with permission from zhang et al . copyright 2014 american chemical society . ( d ) dna nanostructures for the transdermal delivery of dox . [SEP]

[CLS] the 17 - nm dna tetrahedra enabled the dox to reach ~ 400 mm beneath the surface of mouse skin . reproduced with permission from wiraja et al . copyright 2019 springer nature . [SEP]

[CLS] can deliver a different amount of drug molecules . [SEP]

[CLS] moreover , carriers of difference sizes may follow multiple endocytic pathways and result in potential side effects . [SEP]

[CLS] the drug - loading ratio can be accurately controlled by covalently integrating drug molecules into dna oligonucleotides that further self - assemble into shape - defined nanostructures . [SEP]

[CLS] fu and cpt were incorporated into dna strands composing dna nanocages B-nanoparticle , showing an improved efficacy in inhibiting the growth of hela and hct166 tumors B-material in vivo , respectively . [SEP]

[CLS] using dna origami as drug - delivery vehicles B-material was demonstrated in vivo by delivering dox - loaded triangular dna origami to nude mice bearing human orthotopic breast ( mda - mb - 231 ) tumors B-material ( figure 4c ) . [SEP]

[CLS] the triangular dna origami passively accumulated in the tumor B-material region due to the abnormal permeability of tumor B-material vessels and the lack of effective lymphatic drainage , an effect called enhanced permeability and retention ( epr ) . [SEP]

[CLS] besides conventional drug - delivery strategy , which relies on the degradation of carriers and the passive release of the cargo in the endocytic pathway , various triggered - release mechanisms have been implemented with dna - based carriers in vivo . [SEP]

[CLS] a telomeraseresponsive dna icosahedron nanostructure was designed to encapsulate and deliver platinum B-material nanodrugs into cisplatin B-material - resistant human gastric carcinomas ( bgc823 / ddp ) cells B-material for in vivo tumor B-material inhibition . [SEP]

[CLS] atp - responsive nanogels , h 2 o 2 - degradable dna nanoflowers , and self - catabolic dnazyme nanosponges were programmed to release dox in response to atp , h 2 o 2 , or an acidic microenvironment in order to inhibit human breast adenocarcinoma ( mda - mb - 231 ) , human colon cancer ( hct - 166 ) , and subcutaneous hela tumors B-material , respectively . [SEP]

[CLS] most in vivo chemotherapeutic systems were conducted via systemic administration ( e . g . , intravenous injection ) . [SEP]

[CLS] report on the transdermal delivery of dox with dna nanostructures provides new insights into topical , noninvasive drug - delivery methods ( figure 4d ) . [SEP]

[CLS] the 17 - nm dna tetrahedron can deliver dox to 400 mm from the surface of mouse skin , inhibiting melanoma tumor B-material growth with comparable efficacy to intratumoral injection and microneedle application of dox . [SEP]

[CLS] overall , dna nanotechnology provides abundant structural and functional modules for improving the safety , specificity , and efficacy of chemotherapy . [SEP]

[CLS] combining chemotherapy with other therapeutic strategies could further enhance its therapeutic potency . [SEP]

[CLS] combination therapy will be discussed later in this section . [SEP]

[CLS] gene therapy can be achieved via the delivery of healthy genes or gene regulators into abnormal cells B-material for disease prevention or treatment . [SEP]

[CLS] dna nanotechnology facilitates gene therapy via a nonviral delivery of gene regulators that include antisense dna ( asd ) , dnazyme , and small interfering rna ( sirna ) for post - transcriptional gene silencing . [SEP]

[CLS] to prevent the translation of undesirable proteins B-material , asd , dnazyme , and sirna mediate the degradation of target messenger rna ( mrna ) via different mechanisms : asd induces the hydrolysis of targeted mrna by rnase h , dnazyme recognizes and cleaves mrna at a specific site , and sirna induces mrna degradation by forming the rna - induced silencing complex ( risc ) . [SEP]

[CLS] poor cellular uptake of these nucleic B-material - I-material acid I-material gene regulators is a major issue that limits efficient gene silencing . [SEP]

[CLS] dna nanotechnology provides various types of carriers , which can be easily loaded with nucleic B-material - I-material acid I-material gene regulators and internalized via the endocytic pathway . [SEP]

[CLS] as compared with asd alone , integrating asd onto a dna tetrahedron doubled its uptake and gene silencing effect ( figure 5a ) . [SEP]

[CLS] to increase the amount of cargos that can reach the cytoplasm via the endocytic pathway , carriers with a higher loading capacity are preferred for asd delivery . [SEP]

[CLS] for example , multifunctional nanogels , which integrate asd , dnazyme , aptamer , and glutathione ( gsh ) - responsive disulfide B-property linkage I-property , can downregulate genes that are associated with the proliferation of human lung adenocarcinoma epithelial ( a549 ) cells B-material in a targeted and stimulus - responsive manner . [SEP]

[CLS] rna interference ( rnai ) has become a ubiquitous tool in biological research and a new frontier for therapeutics due to its structural simplicity , stealth administration , and universality . [SEP]

[CLS] sirnas can be delivered by various dna nanostructures and downregulate proteins B-material such as survivin and bcl2 , which are involved in apoptosis B-event inhibition of skov - 3 and dms53 cells B-material , respectively . [SEP]

[CLS] ideally , if the nucleic B-material acid I-material cargo can be directly delivered into the cytosol , the dose requirement could be greatly reduced . [SEP]

[CLS] covalently modifying sirna or asd with a disulfide group at its terminus or packaging asd with a guanidinium - disulfide monomer B-material can facilitate a transmembrane delivery to the cytoplasm within 30 min after administration . [SEP]

[CLS] these strategies have the potential to be implemented into dna nanostructures for ultrafast cytosolic delivery of cargos . [SEP]

[CLS] most of the in vivo gene therapy experiments are based on rnai . [SEP]

[CLS] one of the biggest challenges for the implementation of gene therapy in vivo is maintaining the structural integrity of the therapeutic nucleic B-material acids I-material during delivery . [SEP]

[CLS] dna tetrahedra were initially used as a scaffold to organize sirna and folate with well - defined location , density , and spatial orientation for targeted gene silencing of firefly - luciferase - expressing kb xenografts ( figure 5b ) . [SEP]

[CLS] the assembled carrier circulated 4 times longer in the blood than the sirna alone and resulted in a 60 % reduction in the bioluminescent B-property intensity without a detectable immune response . [SEP]

[CLS] microsponges and nanogels are also capable of sirna delivery for the effective knockdown of firefly luciferase in t22 - luc tumor - bearing mice and polo - like kinase 1 ( plk1 ) expression in mda - mb - 231 tumor B-material - bearing mice , respectively . [SEP]

[CLS] in these particles , dna mainly serves as an rna transcription B-event template ( b ) folate - modified dna tetrahedra were used for the targeted delivery of sirna to kb xenograft tumors B-material in vivo . [SEP]

[CLS] the spatial organization of folate on the dna tetrahedra plays an important role in determining the efficiency of gene silencing . [SEP]

[CLS] reproduced with permission from lee et al . copyright 2012 springer nature . [SEP]

[CLS] ( c ) sirna delivery by sst carriers for bcl2 depletion in vivo . [SEP]

[CLS] efficient uptake of a small rectangular structure led to an effective inhibition of dms53 tumor B-material growth in vivo . [SEP]

[CLS] reproduced with permission from rahman et al . copyright 2017 wiley - vch . [SEP]

[CLS] ( d ) crispr - cas9 delivery by using pei - coated dna nanoclews for genome editing . [SEP]

[CLS] egfp depletion was observed in ~ 25 % of u2os . egfp cells B-material after intratumoral injection . [SEP]

[CLS] rca , rolling circle amplification . [SEP]

[CLS] reproduced with permission from sun et al . copyright 2012 wiley - vch . [SEP]

[CLS] or sirna anchoring point [SEP]

[CLS] in the first report of using sst nanocarriers for therapeutics , a set of rectangular and tubular sst nanostructures were screened to deliver sirna for the depletion of an antiapoptotic protein B-material , bcl2 ( figure 5c ) . [SEP]

[CLS] efficient uptake of the smallest rectangular structure led to a 90 % knockdown of the bcl2 protein B-material in vitro and an effective inhibition of dms53 tumor B-material growth in vivo . [SEP]

[CLS] an intriguing example of genome editing was demonstrated by the intratumoral injection of cas9 / sgrna - loaded dna nanoclews for targeted enhanced green fluorescent B-property protein B-material ( egfp ) disruption ( figure 5d ) . [SEP]

[CLS] the successful delivery of crispr - cas9 by dna nanocarriers suggested new opportunities for integrating molecular - biology techniques with the dna nanotechnology platform . [SEP]

[CLS] smart carriers with specific targeting and triggered release functions are in high demand for gene therapy and combination therapy . [SEP]

[CLS] photodynamic therapy ( pdt ) and photothermal therapy ( ptt ) are the two major forms of phototherapies that have been advanced by dna nanotechnology . [SEP]

[CLS] dna carriers improve the solubility B-property , specificity , and cellular uptake of photosensitizers B-property and photothermal materials , and promote reactive oxygen B-material species ( ros ) or heat generation upon irradiation to damage malignant cells B-material . [SEP]

[CLS] compared with chemotherapy , phototherapy is less likely to cause drug resistance , long - term toxicity B-property , and side effects . [SEP]

[CLS] aptamer - photosensitizer B-property complexes such as aptamer - chlorin B-material e6 ( ce6 ) conjugates and porphyrin photosensitizer B-property ( tmpyp4 ) - loaded aptamers were the earliest constructs for targeted pdt . [SEP]

[CLS] aptamers confine photosensitizers B-property to malignant cells B-material and minimize the indiscriminate damage of ros on healthy cells B-material . [SEP]

[CLS] the pdt effect can be locally amplified with the use of a catalytic dna circuit , where the catalystsequence - bearing aptamer activates and catalyzes the revelation of ce6 on the cell B-material surface . [SEP]

[CLS] moreover , different aptamers can be multiplexed in a single circuit for logic - based cell B-material recognition and pdt . [SEP]

[CLS] for example , a 3 - arm dna ' ' nanoclaw ' ' carrying an sgc8c aptamer , a tc01 aptamer , and a ce6 photosensitizer B-property on each arm could operate based on the and logic gate and activate ce6 only when both aptamers recognized targeted surface markers on the same cell B-material ( figure 6a ) . [SEP]

[CLS] dna origami can improve the solubility B-property and photostability of bmepc , a carbazolederived photosensitizer B-property , and enhance radical production in mcf - 7 cells B-material ( figure 6b ) . [SEP]

[CLS] photothermal materials are usually bulkier and less programmable than photosensitizers B-property ; therefore , among all types of dna nanostructures , dna origami is usually used as the carrier for ptt . [SEP]

[CLS] compared with chemo - and gene therapy , there are not as many applications of dna nanotechnology - based phototherapy in vivo . [SEP]

[CLS] dna nanosponges were loaded with sgc8c aptamer , catalase , and tmpyp4 photosensitizer B-property to achieve effective pdt under hypoxic conditions ( figure 6c ) . [SEP]

[CLS] the sensitization of pdt could be enhanced by including the antisense sequence - targeting hypoxia - inducible factor 1a ( hif - 1a ) , a major transcription B-event factor associated with tumor B-material hypoxia . [SEP]

[CLS] the passive tumor B-material - targeting property of dna origami has been used to assist the delivery of gold B-material nanorods B-nanoparticle ( aunrs ) to the tumor B-material site for a more efficient elevation of local temperatures upon near - infrared ( nir ) irradiation and for better ptt efficacy than aunr itself ( figure 6d ) . [SEP]

[CLS] integrating imaging agents into these therapeutic systems enabled a real - time visualization of their biodistribution and tumor B-material uptake via fluorescence B-property or optoacoustic imaging . [SEP]

[CLS] in summary , dna nanotechnology primarily enhances the specificity and efficacy of phototherapy . [SEP]

[CLS] combining phototherapy with other therapeutic strategies could result in a more synergistic effect and light - controlled drug release . [SEP]

[CLS] unmethylated cytosine - phosphate - guanine ( cpg ) oligonucleotides with certain sequence motifs can be recognized by toll - like receptor B-material 9 ( tlr9 ) and stimulate cytokine release and an immune response . [SEP]

[CLS] tlr9 is expressed in antigen - presenting cells B-material ( apcs ) and is generally located in the endosome . [SEP]

[CLS] since dna nanostructures are usually internalized into apcs via the endocytic pathway , the delivery of synthetic cpg oligonucleotides by dna nanostructures is a convenient method for immune stimulation and immunotherapy . [SEP]

[CLS] cellular delivery of well - studied synthetic cpg motifs has been achieved with a variety of dna nanocarriers , including y - shaped tiles , dendrimers B-nanoparticle , hydrogels , dna tetrahedra , and dna origami tubes ( figure 7a ) . [SEP]

[CLS] as indicated by enzymelinked immunosorbent assay ( elisa ) , compared with cpg motif itself , a significantly higher level of cytokines ( e . g . , tumor B-material necrosis factor ( tnf ) - a , interleukin ( il ) - 6 , and il - 12 ) can be induced by the cpg motif delivered by dna nanocarriers . [SEP]

[CLS] the cytokine levels were positively correlated with the number of cpg motifs displayed on a single dna tetrahedron . [SEP]

[CLS] the activation of immune cells B-material induced by dna origami tubes carrying 62 cpg sequences was also indicated by a greater amount of the early activation marker cd69 on dendritic and b cells B-material . [SEP]

[CLS] a synthetic vaccine was rationally designed by precisely assembling cpg adjuvants and a model antigen , streptavidin ( stv ) , onto dna tetrahedra ( figure 7a ) . [SEP]

[CLS] the vaccine mimicked a natural viral particle , inducing an antibody B-material response against stv and maintaining a higher anti - stv igg level than that of free cpg and stv for the photosensitizer B-property ( green triangle ) is activated only when both targeting domains are attached to the surface biomarkers B-property on cancer cells B-material . reproduced with permission from you et al . copyright 2014 american chemical society . [SEP]

[CLS] ( b ) dna origami for photosensitizer B-property delivery into tumor B-material cells B-material . [SEP]

[CLS] the model photosensitizer B-property , bmepc , can be loaded onto dna origami by intercalation . [SEP]

[CLS] dna origami reduces the photobleaching of bmepc and enhances its radical production . [SEP]

[CLS] reproduced with permission from zhuang et al . copyright 2016 american chemical society . ( c ) dna nanosponges for enhanced pdt . [SEP]

[CLS] co - delivery of tmpyp4 and catalase by dna nanosponges can relieve hypoxia - associated resistance and enhance the efficacy of tmpyp4 . [SEP]

[CLS] reproduced with permission from pan et al . copyright 2019 wiley - vch . [SEP]

[CLS] ( d ) aunr delivery by dna origami . [SEP]

[CLS] optoacoustic imaging and photothermal therapy are simultaneously achieved in vivo . [SEP]

[CLS] reproduced with permission from du et al . copyright 2016 wiley - vch . [SEP]

[CLS] over 70 days . [SEP]

[CLS] to prevent postsurgical tumor B-material relapse , an anti - pd - 1 antibody B-material was encapsulated in a cpg - encoded nano - cocoon and locally injected into the resection bed . [SEP]

[CLS] a local proinflammatory environment triggered the sustained release of cpg oligonucleotides and anti - pd - 1 antibodies B-material , inducing an antitumor effect that was effective for both remaining and metastatic tumors B-material . [SEP]

[CLS] overall , the use of dna nanotechnology for immunotherapy mainly focuses on cpg delivery . [SEP]

[CLS] recently , ( c ) a prototype dna nanorobot for triggered cargo exposure based on and logic . [SEP]

[CLS] the sequestered antibody B-material fragments are exposed for cell B-material signaling regulation when both aptamerbased locks are attached to the corresponding cell B-material surface markers . [SEP]

[CLS] reproduced with permission from douglas et al . copyright 2012 aaas . [SEP]

[CLS] ( d ) a nucleolin - responsive dna nanorobot for tumor B-material inhibition in vivo . [SEP]

[CLS] the blood B-event coagulation I-event protease , thrombin , is exposed in response to nucleolin and induces intravascular thrombosis to inhibit tumor B-material growth . reproduced with permission from li et al . copyright 2018 springer nature . [SEP]

[CLS] ( e ) dna origami with preferred renal uptake and aki alleviation effect . [SEP]

[CLS] compared with dna origami with other geometries , rectangular dna origami showed an outstanding ros - scavenging effect , which was further used for aki treatment . [SEP]

[CLS] reproduced with permission from jiang et al . copyright 2018 springer nature . [SEP]

[CLS] aptamer - equipping strategies for immune - cell B-material engineering started to emerge , which hold great potential in adoptive immunotherapy . [SEP]

[CLS] therapeutic agents kill malignant cells B-material with chemical toxicity B-property , biological interference , or physical damage . [SEP]

[CLS] however , intrinsic limitations and adverse effects could still cause a simple therapeutic strategy to fail . [SEP]

[CLS] for example , tumor B-material cells B-material could potentially develop resistance to chemotherapy . [SEP]

[CLS] phototherapy has limited tissue - penetration depth and limited efficacy on metastatic cancer . [SEP]

[CLS] gene therapy is usually short lived and might incite an immune response . [SEP]

[CLS] to address these issues , dna nanotechnology provides a multifunctional platform that integrates therapeutic strategies into a single formulation to promote a synergistic effect of different strategies ( figure 7b ) . [SEP]

[CLS] moreover , the dose and ratio of therapeutic agents can be finely tuned on the dna platform , minimizing dose - dependent toxicity B-property and other side effects without compromising efficacy . [SEP]

[CLS] combination therapy has been proven to be effective against mdr cancer cells B-material . [SEP]

[CLS] for example , dox and the gene encoding tumor B-material suppressor p53 were delivered into mdr cancer ( mcf - 7r ) cells B-material by a triangular dna origami to inhibit tumor B-material growth without eliciting apparent systemic toxicity B-property or immune response . [SEP]

[CLS] dox , aunr , and muc1 aptamer have been combined on a triangular dna origami for targeted photo - chemo therapy in vitro . [SEP]

[CLS] the photothermal effects of aunr upon nir irradiation inhibited the expression of glycoprotein ( p - gp ) , a typical drug efflux pump involved in drug resistance , and enhanced the efficacy of dox on dox - resistant mcf - 7 / adr cells B-material . [SEP]

[CLS] another widely used formulation is the co - delivery of chemotherapy drug along with gene regulators targeting p - gp . [SEP]

[CLS] the cytotoxic B-property effect of dox on mdr tumors B-material can be effectively enhanced by various p - gp inhibitors , including asd nanoparticles B-nanoparticle and small - hairpin rna ( shrna ) transcription B-event templates [SEP]

[CLS] combination therapy explores the complementary and synergistic effects among a combination of therapeutic strategies , providing potential solutions for tumor B-material types that are difficult to treat with a single therapy . [SEP]

[CLS] therapeutic dna nanorobots therapeutic dna nanorobots are dna devices that can automatically perform therapeutic tasks , including target recognition , drug delivery , and triggered release , following pre - encoded rules . [SEP]

[CLS] for example , a prototype dna nanorobot was programmed to open and expose its payloads in response to a combination of ' ' key ' ' antigens that were present on the surface of a cell B-material ( figure 7c ) . [SEP]

[CLS] by varying its payloads , the nanorobot could carry out user - defined tasks such as cell B-material discrimination , growth arrest of aggressive natural killer leukemia ( nkl ) cells B-material , and t cell activation . [SEP]

[CLS] recently , therapeutic dna nanorobot was successfully applied to cancer therapy in vivo ( figure 7d ) . [SEP]

[CLS] rather than being internalized into tumor B-material cells B-material , the nanorobot was activated in response to nucleolin in the tumor B-material vessel and subsequently exposed thrombins that were initially sequestered to trigger intravascular thrombosis at the tumor B-material site and induced tumor necrosis . [SEP]

[CLS] no significant changes in the blood B-event coagulation I-event parameters , cytokine levels , or cytotoxicity B-property were observed when testing the nanorobot in healthy mice and bama miniature pigs , suggesting that their use in the normal tissues of large animals would be considered safe . [SEP]

[CLS] the kidney is an important organ that filters blood , removes wastes and toxins , maintains the balance of body fluids and electrolytes , and helps control blood pressure in animal bodies . [SEP]

[CLS] kidney dysfunction can lead to serious or even life - threatening health issues . [SEP]

[CLS] several recent studies that highlight the potential of applying dna nanotechnology to the treatment of kidney diseases ( or nephropathy ) are discussed here . [SEP]

[CLS] there are various biological interfaces in living bodies , which form the barriers B-property for drug delivery and affect the organ distribution of nanoparticles B-nanoparticle . [SEP]

[CLS] given the extraordinary programmability of dna nanostructures , one may envision that their abilities to pass through biological barriers B-property and target specific organs ( e . g . , brain , liver , kidney , etc . ) can be improved by simply tuning their physical properties . [SEP]

[CLS] in general , nanoparticles B-nanoparticle ranging from 30 to 150 nm are not easily cleared by kidney filtration , while those with a small hydrodynamic size ( 5 - 7 nm ) or with high aspect ratios and small diameters can be cleared as they fall below the filtration threshold of kidney . [SEP]

[CLS] taking advantage of this effect , dna nanostructures can be designed to have distinct renal uptake and retention profiles . [SEP]

[CLS] for example , the renal clearance of cu 64 - labeled small dna tetrahedra ( 7 nm ) can be monitored for the evaluation of kidney functions via positron B-technique emission I-technique tomography I-technique ( pet ) imaging . [SEP]

[CLS] in another study , pet imaging of the biodistribution of cu 64 - labeled dna origami nanostructures revealed that intact structures preferentially accumulate in kidneys within 12 h and showed whole - body clearance after 24 h postinjection . [SEP]

[CLS] in contrast , the scaffold strand and partially folded dna origami nanostructures were primarily sequestered in the liver and cleared by the mononuclear phagocyte system . [SEP]

[CLS] thus , structural compactness and intact folding are two factors that reduce hepatic sequestration and improve kidney accumulation of dna nanostructures . [SEP]

[CLS] treating aki with dna nanostructures kidney diseases can be generally categorized into acute kidney injury ( aki ) , chronic kidney disease ( ckd ) , and kidney - related diseases ( e . g . , kidney tumor B-material ) . [SEP]

[CLS] a rectangular dna origami was exploited to alleviate rhabdomyolysis - induced aki and protect renal cells B-material from nephrotoxic agents ( figure 7e ) . [SEP]

[CLS] its therapeutic effect was evaluated by dynamic pet imaging I-technique with ga - edta , blood tests , and kidney - tissue staining , which was similar to antioxidant B-property n - acetylcysteine , a clinical drug for contrast - induced aki prevention . [SEP]

[CLS] current research suggests the preferential renal uptake and the possibility of tuning the retention of dna nanostructures in kidneys . [SEP]

[CLS] therefore , it is possible to apply dna - based therapeutic formulations that have been proven effective in vivo to the treatments of other kidney diseases . [SEP]

[CLS] the key is to find target molecules that are involved in the onset of kidney diseases . [SEP]

[CLS] in addition to ros , potential targets include noncoding rnas , and proteins B-material such as kidney injury molecule - 1 ( kim - 1 ) , clusterin and transforming growth factor - b ( tgf - b ) [SEP]

[CLS] based on these targets , it is possible to design proper kidney - targeted dna drug delivery systems for the treatment of other kidney diseases . [SEP]

[CLS] in the past decade , remarkable progress has been made in structural dna nanotechnology , which facilitates the use of designer dna nanostructures for therapeutic applications . [SEP]

[CLS] complex higher - order dna assemblies can be rationally and automatically designed and efficiently scaled - up . [SEP]

[CLS] chemical methods are developed to enhance the stability of dna nanostructures in physiological environments . [SEP]

[CLS] synthesis and purification costs of dna origami structures are expected to be greatly reduced by the recently reported mass - production and purification protocols . [SEP]

[CLS] the modularity and programmability of the dna platform allow various mechanisms of target recognition and triggered release to be implemented in vivo . [SEP]

[CLS] several challenges still remain to be addressed before using dna nanocarriers in clinical practice . [SEP]

[CLS] firstly , the structural heterogeneity of dna nanocarriers may cause side effects . [SEP]

[CLS] there is evidence that partially formed and intact dna nanostructures have different preferences for organ accumulation . [SEP]

[CLS] it can be inferred that the organ - targeting ability of a dna nanocarrier changes during circulation due to its gradual denaturation . aberrant accumulation not only increases the burdens of healthy organs but also reduces the effective concentration of the drug at pathogenic sites . [SEP]

[CLS] moreover , precise dosing is challenging to achieve , especially for intercalating drugs , whose spectrum properties and loading and release profiles are affected by a number of factors . [SEP]

[CLS] in this respect , a gold B-material standard is needed to enable cross - comparison between studies . [SEP]

[CLS] drug - loading capacity can be better controlled by covalently conjugating drug molecules onto dna strands that compose a nanocarrier . [SEP]

[CLS] biotechnological methods for the economical synthesis of drug - conjugated dna rely on the enzymes that can catalyze the polymerization of nucleotide - containing unnatural base analogs . [SEP]

[CLS] although there are in vitro strategies available , in vivo production is largely elusive . [SEP]

[CLS] secondly , changes in the surface chemistry of dna nanocarriers may affect their biodistribution . [SEP]

[CLS] for example , surface coating B-material via electrostatic interaction is likely to change the circulating time , organ distribution , and toxicity B-property of a dna nanostructure . [SEP]

[CLS] the resultant effects need to be characterized in vivo . [SEP]

[CLS] protein B-material - corona I-material formation is another factor that could drastically alter the surface chemistry of dna nanostructures in vivo . [SEP]

[CLS] serum proteins B-material can adhere to dna nanostructures in both sequence - dependent and nonspecific manners , and further induce aggregation or promote clearance . [SEP]

[CLS] to solve this problem , chemical modification and coating B-material could effectively change the surface chemistry of dna nanostructures and prevent protein B-material - corona I-material formation by reducing the affinity of serum proteins B-material . [SEP]

[CLS] alternatively , the sequence of dna nanostructures can be rationally designed to alter the profile of protein B-material adsorption and facilitate organ targeting . [SEP]

[CLS] moreover , the endocytosis B-event mechanism of dna nanostructures is not comprehensively understood . [SEP]

[CLS] although dna nanotechnology has the unique advantage of designing arbitrary shapes with nanometer precision , the types of dna nanostructures that have been tested for endocytosis B-event are relatively limited . [SEP]

[CLS] comprehensive mechanistic studies that take structure characteristics , surface chemistry , and cell B-material type into account are needed to predict the endocytosis B-event and cellular fate of a specific construct . [SEP]

[CLS] getting trapped and degraded in the lysosome is usually the fate of internalized dna nanostructures . [SEP]

[CLS] therefore , simple and robust strategies to facilitate endo / lysosomal escape , organelle targeting , and nuclear entry are in demand . [SEP]

[CLS] exploring nonendocytic pathway for dna nanostructures to circumvent the acidic environment in the lysosome will greatly enhance the efficacy of therapeutic agents that function in the cytosol and nucleus . [SEP]

[CLS] given the complex environments in vivo , the pharmacokinetics and pharmacodynamics of dna nanostructures are complicated by many factors . [SEP]

[CLS] tracing the absorption , distribution , metabolism , and excretion of a dna carrier and its cargo , as well as their effects on living organisms , are the key to evaluate dosing , efficacy , and adverse effects . [SEP]

[CLS] rapid clearance is a major obstacle that limits the efficacy of dna - based drug - delivery systems at the current stage of research . [SEP]

[CLS] a higher cost and toxicity B-property will be associated with the repetitive administration of drugs at a higher dose to prolong the retention time . [SEP]

[CLS] finally , the biosafety of dna - based therapeutic systems should be evaluated in the long term . [SEP]

[CLS] for example , the contamination of immunostimulatory endotoxin , which is involved in the preparation and amplification of dna from gram - negative bacteria , must be evaluated and reduced to the safe level . [SEP]

[CLS] there is no indication of chronic toxicity B-property induced by dna nanostructures so far , which can be largely attributed to the rapid clearance of dna nanostructures from the body . [SEP]

[CLS] extending the retention of dna nanostructure might bring new safety concerns . [SEP]

[CLS] for example , given the complexity and randomness of dna sequences in a nanostructure , extraneous dna could randomly interfere with cellular rna and induce other potential chronic toxicity B-property . [SEP]

[CLS] moreover , the immune response has not been well characterized for dna nanostructures in vivo . [SEP]

[CLS] although many studies report that cpg - free dna nanostructures have minimal immunogenicity B-property , immunostimulatory activity via tlr9 - independent pathway is not negligible . [SEP]

[CLS] principles to design dna carriers that are compatible with the immune system of higher organisms are in need . [SEP]

[CLS] recent advances in dna nanotechnology - based therapeutics have brought up new opportunities for future research . [SEP]

[CLS] first , to obtain a general and comprehensive understanding of the endocytosis B-event mechanism and the pharmacokinetics and pharmacodynamics of dna nanostructures , it is necessary to summarize individual therapeutic examples into networks in order to better predict the interaction between dna nanostructures and living organisms . [SEP]

[CLS] big data analytics and machine learning could help with the exploration of the vast design space for this purpose . [SEP]

[CLS] second , more diverse drug - administration routes are in demand . [SEP]

[CLS] the successful implementation of transdermal dox delivery suggests the possibilities of developing other noninvasive drug - delivery routes such as intranasal administration . [SEP]

[CLS] topical administration via mucosa is expected to yield rapid drug absorption and reduced risk of systemic side effects , and may serve as a supplementary of radiation therapy for nasopharyngeal carcinoma and other diseases . [SEP]

[CLS] third , the ability to pattern diverse molecules with nanometer precision would facilitate the rational design of antivirals B-property or vaccines . [SEP]

[CLS] for example , a practical strategy to engineer antivirals B-property is to block and deactivate viruses with patterned ligands that are templated by a dna scaffold . [SEP]

[CLS] another example is the effective b cell receptor B-material activation in vitro by sitespecifically displaying immunogens B-property on a dna template . [SEP]

[CLS] implementation of these two systems in vivo remains to be explored . [SEP]

[CLS] fourth , dna nanostructure has the potential to be used as an immunosuppressant to regulate the excessive release of cytokines . [SEP]

[CLS] this is helpful for alleviating cytokine storm , which is a catastrophic immune problem that may cause permanent organ damage or even death . [SEP]

[CLS] at last , replicable single - stranded dna origami structures are promising candidates for therapeutics as they have suitable size , addressability , and exceptional thermostability . [SEP]

[CLS] dna nanotechnology - based therapeutics will certainly benefit from the development of new drugs , therapeutic strategies , and formulations . [SEP]

[CLS] solutions to intractable solid tumors B-material and vascularized metastases B-event will be promising to pursue . [SEP]

[CLS] as a rapidly evolving research direction , dna nanotechnology - based therapeutics would serve as a smart , custom platform for clinical therapeutics . [SEP]

[CLS] 1 . a timeline of the field and the emerging therapeutic applications of dna nanotechnology ( a ) a timeline of the field of structural dna nanotechnology since 1982 . [SEP]

[CLS] ( b ) a timeline of the emerging therapeutic applications of dna nanotechnology since 2008 . [SEP]

[CLS] representative discoveries and achievements are listed . [SEP]

[CLS] sst , single - stranded tile ; dox , doxorubicin B-material ; ros , reactive oxygen B-material species . [SEP]

[CLS] structural dna nanotechnology ( a ) ned ' s original concept : forming a 2d lattice from immobile junctions through complementary sticky ends . [SEP]

[CLS] reproduced with permission from seeman . [SEP]

[CLS] copyright 1982 elsevier . [SEP]

[CLS] ( b ) discrete nanoobjects can be assembled from oligonucleotides with rationally designed sequences and complementarities . [SEP]

[CLS] a ~ 7 nm dna cube is the earliest polyhedral object constructed from dna . [SEP]

[CLS] ( c ) dna tile - based self - assembly is a feasible approach to create higher - order structures from modular building blocks . [SEP]

[CLS] for example , a 4 - by - 4 dna tile can be assembled from several oligonucleotides and further linked into 2d lattices through complementary sticky ends . [SEP]

[CLS] ( d ) dna origami is the folding of a long , single - stranded dna ( termed ' ' scaffold ' ' ) into 2d or 3d shapes with the help of hundreds of short dna oligonucleotides ( termed ' ' staples ' ' ) . [SEP]

[CLS] ( top right ) reproduced with permission from rothemund . [SEP]

[CLS] copyright 2006 springer nature . [SEP]

[CLS] ( bottom right ) reproduced with permission from castro et al . copyright 2011 springer nature . [SEP]

[CLS] ( e ) single - stranded tiles ( ssts ) can be programmed to assemble into 2d or 3d shapes without the guidance of a scaffold . [SEP]

[CLS] ssts interact with each other through complementary domains , in a way analogous to ' ' lego ' ' bricks . [SEP]

[CLS] ( top right ) reproduced with permission from wei et al . copyright 2012 springer nature . [SEP]

[CLS] ( bottom right ) reproduced with permission from ke et al . copyright 2012 aaas . [SEP]

[CLS] ( f ) single - stranded dna origami is the unimolecular folding of a long single - stranded dna into nanostructures through paranemic cohesions . [SEP]

[CLS] reproduced with permission from han et al . copyright 2017 aaas . [SEP]

[CLS] 1156 - 1179 , may 13 , 2021 1159 [SEP]

[CLS] criteria for developing dna - based nanocarriers ( a ) common strategies to stabilize dna nanostructures under physiological conditions . [SEP]

[CLS] unmodified dna nanostructures are usually susceptible to cation B-material depletion and enzyme digestion due to the charge repulsion between negatively charged dna backbones and the existence of nick points between individual strands . [SEP]

[CLS] ligation of nick points , cross - linking , and surface coating B-material are widely used strategies for protecting dna nanostructures from denaturation or degradation under physiological conditions . [SEP]

[CLS] ( b ) illustration depicting the cellular uptake pathways of dna nanostructures . [SEP]

[CLS] a dna tetrahedron ( 7 nm ) and a dna origami rod ( 127 nm in length ) are both internalized into hela cells B-material via caveolaemediated endocytosis B-event . [SEP]

[CLS] a dna nanoribbon with a high aspect ratio takes the clathrin - mediated endocytic pathway into h460 cells B-material . [SEP]

[CLS] the disulfide - modified dna nanospheres B-nanoparticle are directly internalized into the cytosol of hela cells B-material through a nonendocytic pathway . [SEP]

[CLS] ( c ) a variety of targeting modules , including aptamer , antibody B-material , small - molecule ligand , peptide B-material , and protein B-material , have been integrated onto dna - based carriers , resulting in improved targeting specificity and cellular uptake efficiency . [SEP]

[CLS] 4 . dna nanotechnology for chemotherapy ( a ) tuning the loading capacity and releasing rate of dox by varying the global twist of dna origami nanotubes B-nanoparticle . [SEP]

[CLS] dox can be easily loaded onto dna nanostructures by intercalating between base pairs . [SEP]

[CLS] twisted dna origami nanotubes B-nanoparticle with 12 bp / turn showed a higher loading capacity and a more sustained release , compared to straight ones with 10 . 5 bp / turn . [SEP]

[CLS] reproduced with permission from zhao et al . copyright 2012 american chemical society . [SEP]

[CLS] ( b ) muc1 aptamer - modified dna icosahedra for targeted delivery of dox into mcf - 7 cells B-material . [SEP]

[CLS] reproduced with permission from chang et al . copyright 2011 american chemical society . [SEP]

[CLS] ( c ) dna origami for dox delivery in vivo . [SEP]

[CLS] dox - loaded dna origami showed passive tumor B-material accumulation and antitumor efficacy without observable systemic toxicity B-property . [SEP]

[CLS] reproduced with permission from zhang et al . copyright 2014 american chemical society . [SEP]

[CLS] ( d ) dna nanostructures for the transdermal delivery of dox . [SEP]

[CLS] the 17 - nm dna tetrahedra enabled the dox to reach ~ 400 mm beneath the surface of mouse skin . [SEP]

[CLS] reproduced with permission from wiraja et al . copyright 2019 springer nature . [SEP]

[CLS] dna nanotechnology for gene therapy ( a ) nonviral delivery of aso and dnazyme by a dna tetrahedron for post - transcriptional gene silencing . [SEP]

[CLS] dna nanocarriers enhance the cellular uptake of aso and dnazyme . [SEP]

[CLS] aso and dnazyme inhibit downstream protein B-material production by degrading the corresponding mrna . ( b ) folate - modified dna tetrahedra were used for the targeted delivery of sirna to kb xenograft tumors B-material in vivo . [SEP]

[CLS] the spatial organization of folate on the dna tetrahedra plays an important role in determining the efficiency of gene silencing . [SEP]

[CLS] reproduced with permission from lee et al . copyright 2012 springer nature . [SEP]

[CLS] ( c ) sirna delivery by sst carriers for bcl2 depletion in vivo . [SEP]

[CLS] efficient uptake of a small rectangular structure led to an effective inhibition of dms53 tumor B-material growth in vivo . [SEP]

[CLS] reproduced with permission from rahman et al . copyright 2017 wiley - vch . [SEP]

[CLS] ( d ) crispr - cas9 delivery by using pei - coated dna nanoclews for genome editing . [SEP]

[CLS] egfp depletion was observed in ~ 25 % of u2os . egfp cells B-material after intratumoral injection . [SEP]

[CLS] rca , rolling circle amplification . [SEP]

[CLS] reproduced with permission from sun et al . copyright 2012 wiley - vch . [SEP]

[CLS] 6 . dna nanotechnology for phototherapy ( a ) a logic - based dna nanoclaw for cancer targeting and pdt . [SEP]

[CLS] the photosensitizer B-property ( green triangle ) is activated only when both targeting domains are attached to the surface biomarkers B-property on cancer cells B-material . [SEP]

[CLS] reproduced with permission from you et al . copyright 2014 american chemical society . [SEP]

[CLS] ( b ) dna origami for photosensitizer B-property delivery into tumor B-material cells B-material . [SEP]

[CLS] the model photosensitizer B-property , bmepc , can be loaded onto dna origami by intercalation . [SEP]

[CLS] dna origami reduces the photobleaching of bmepc and enhances its radical production . [SEP]

[CLS] reproduced with permission from zhuang et al . copyright 2016 american chemical society . [SEP]

[CLS] ( c ) dna nanosponges for enhanced pdt . [SEP]

[CLS] co - delivery of tmpyp4 and catalase by dna nanosponges can relieve hypoxia - associated resistance and enhance the efficacy of tmpyp4 . [SEP]

[CLS] reproduced with permission from pan et al . copyright 2019 wiley - vch . [SEP]

[CLS] ( d ) aunr delivery by dna origami . [SEP]

[CLS] optoacoustic imaging and photothermal therapy are simultaneously achieved in vivo . [SEP]

[CLS] reproduced with permission from du et al . copyright 2016 wiley - vch . [SEP]

[CLS] other promising therapeutic strategies facilitated by dna nanotechnology ( a ) two strategies of using dna nanostructures for immunotherapy . [SEP]

[CLS] dna nanostructures enhance the cellular uptake of immunostimulatory cpg sequences and induce a high - level secretion of various pro - inflammatory I-property cytokines . [SEP]

[CLS] co - delivery of cpg adjuvants and a model antigen by dna tetrahedra induces strong and long - lasting antibody B-material responses against the model antigen . [SEP]

[CLS] ( top left ) reproduced with permission from li et al . copyright 2011 american chemical society . [SEP]

[CLS] ( bottom left ) reproduced with permission from schuller et al . copyright 2011 american chemical society . [SEP]

[CLS] ( right ) reproduced with permission from liu et al . copyright 2012 american chemical society . [SEP]

[CLS] ( b ) three common strategies for combination therapy . [SEP]

[CLS] combination therapy can be achieved by the co - delivery of two synergistic therapeutic agents by the same dna carrier . [SEP]

[CLS] examples of combination therapy include photo - chemo therapy , chemo - gene therapy , and photothermaldynamic therapy . [SEP]

[CLS] ( c ) a prototype dna nanorobot for triggered cargo exposure based on and logic . [SEP]

[CLS] the sequestered antibody B-material fragments are exposed for cell B-material signaling regulation when both aptamerbased locks are attached to the corresponding cell B-material surface markers . [SEP]

[CLS] reproduced with permission from douglas et al . copyright 2012 aaas . [SEP]

[CLS] ( d ) a nucleolin - responsive dna nanorobot for tumor B-material inhibition in vivo . [SEP]

[CLS] the blood B-event coagulation I-event protease , thrombin , is exposed in response to nucleolin and induces intravascular thrombosis to inhibit tumor B-material growth . [SEP]

[CLS] reproduced with permission from li et al . copyright 2018 springer nature . [SEP]

[CLS] ( e ) dna origami with preferred renal uptake and aki alleviation effect . [SEP]

[CLS] compared with dna origami with other geometries , rectangular dna origami showed an outstanding ros - scavenging effect , which was further used for aki treatment . [SEP]

[CLS] reproduced with permission from jiang et al . copyright 2018 springer nature . [SEP]

[CLS] single - base changes lead to important biological and biomedical implications ; however , the discrimination of single - base changes from normal dna always remains a grand challenge . [SEP]

[CLS] herein we developed a dna recognition and amplification system based on artificial branched dna , namely , target - triggered polymerization ( ttp ) , to realize enzyme - free and fast discrimination of single - base changes . [SEP]

[CLS] branched dna as monomers B-material rapidly polymerized into dna nanospheres B-nanoparticle only with the trigger of specific dna . [SEP]

[CLS] our ttp system worked reliably over a wide range of conditions . [SEP]

[CLS] remarkably , our ttp system was capable of discriminating base - changing dna from normal dna , including distinguishing 1 - 4 nucleotide changes and positions of single base , which was attributed to the significant amplification of small differences in hybridization thermodynamics and kinetics . [SEP]

[CLS] we further proposed a theoretical method for calculating the hybridization probability of nucleic B-material acids I-material , which performed highly consistent with experimental results . [SEP]

[CLS] nucleic B-material acids I-material are genetic biopolymers B-material that are composed of nucleotides , which are essential to all known forms of life . [SEP]

[CLS] alteration of nucleotides between nucleic B-material acid I-material sequences ( single - base substitution ) , as the most common form of nucleic B-material acid I-material variations , is often associated with important biological and biomedical implications . [SEP]

[CLS] for instance , nucleotide changes in the coding region of genome affect the sequences of amino B-material acid I-material and protein B-material function , leading to the occurrence of genetic disease . [SEP]

[CLS] nucleotide changes in the pathogen genome cause antibiotic resistance . [SEP]

[CLS] in addition , tumor - associated base changes have significant impacts on tumor B-material growth , transformations , and metastasis B-event , which can serve as noninvasive biomarkers B-property of cancers . [SEP]

[CLS] it is therefore vitally important to develop effective strategies for the discrimination of single - base changes . [SEP]

[CLS] single - base changes have only one nucleotide difference with normal counterparts ; it is extremely challenging to discriminate single - base - changing dna from normal dna because of the small energetic differences in hybridization reactions . [SEP]

[CLS] dna nanotechnology and the corresponding dna nanostructures with recognition capability and programmability provide strategies for target recognition and signal amplification to increase the small differences ( [SEP]

[CLS] the difficulty of design and use , it is necessary to develop an enzyme - free , simply designed , low - cost , and easily manipulated method for the discrimination of single - base changes . [SEP]

[CLS] herein , we constructed a branched dna - based polymerization system , namely , ' ' target - triggered polymerization ( ttp ) . ' ' [SEP]

[CLS] in ttp system , branched dna was designed to polymerize into dna nanospheres B-nanoparticle only under the trigger of specific dna , realizing target recognition and efficient signal amplification simultaneously . [SEP]

[CLS] our ttp system can be accomplished rapidly without the involvement of any enzymes . [SEP]

[CLS] in addition , the ttp system possessed robust performance in a wide range of conditions . [SEP]

[CLS] our enzyme - free , rapid , and robust ttp system enabled high specificity and sensitivity . [SEP]

[CLS] remarkably , our ttp system was capable of discriminating base - changing dna from normal dna , including different number of nucleotide changes and the positions of single - base change . [SEP]

[CLS] furthermore , thermodynamics and kinetics analyses showed that the ttp system apparently amplified the small differences of base - changing dna with normal dna in an identical hybridization reaction . [SEP]

[CLS] taking advantage of the ttp system , we developed a theoretical model for analyzing the hybridization probability of nucleic B-material acids I-material , which performed highly consistent with experimental results , making our ttp system a powerful tool for exploring the probability of nucleic B-material acid I-material hybridization . [SEP]

[CLS] enzyme - free and fast ttp system for simultaneous target recognition and signal amplification x - shaped branched dna ( x - dna ) was designed as ttp monomers B-material , which consisted of four corresponding single - stranded dna ( ssdna ) . [SEP]

[CLS] through rational sequence design , ssdna was composed of intermolecular binding region ( marked by black in scheme 1a ) for the construction of x - dna and sticky ends ( marked by red ) for recognition with specific target dna ( transfer dna ) . [SEP]

[CLS] four ssdna ( ssdna 1 , ssdna 2 , ssdna 3 , and ssdna 4 ) self - assembled to from x - dna with optimized annealing procedure . [SEP]

[CLS] in ttp system , two types of x - dna ( x 1 and x 2 ) were designed as monomers B-material to further form dna nanospheres B-nanoparticle . [SEP]

[CLS] x 1 and x 2 had the same binding core B-material and different sticky ends , which were complementary with specific t - dna . [SEP]

[CLS] through this design , t - dna functioned both as initiators to trigger the polymerization of x - dna and as linkers to hybridize with x 1 and x 2 , consequently forming dna nanospheres B-nanoparticle ( scheme 1b ) . [SEP]

[CLS] it was notable that the formation of polymeric dna nanospheres B-nanoparticle only occurred in the presence of t - dna . [SEP]

[CLS] in addition , the ttp system did not require any enzymes , reducing the operational complexity and potentially facilitating future applications such as point - of - care testing ( poct ) . [SEP]

[CLS] specifically , compared with other enzyme - free amplification methods , such as hcr and strand displacement reaction , the ttp system avoided the steps of toehold migration and hairpin structure de - conformation , which therefore enabled the formation of dna nanospheres B-nanoparticle in a very short period of time . [SEP]

[CLS] in other words , simultaneous recognition and amplification was achieved in a one - step reaction and in an enzyme - free and rapid manner . [SEP]

[CLS] we first constructed x - dna by mixing four corresponding ssdna at equimolar concentrations and with further annealing procedure . [SEP]

[CLS] the successful synthesis of x - dna was characterized and confirmed by gel B-technique electrophoresis I-technique ( figure s1a ) . [SEP]

[CLS] the addition of t - dna into the mixture of x 1 and x 2 initiated the polymerization of dna nanospheres B-nanoparticle . [SEP]

[CLS] polymeric dna nanospheres B-nanoparticle with higher molecular weights were observed in agarose B-technique gel I-technique electrophoresis I-technique ( figure s1b ) . [SEP]

[CLS] the bands in gel hole indicated the successful synthesis of dna nanospheres B-nanoparticle . [SEP]

[CLS] a long - tail smear in the lanes of x 1 + x 2 + t - dna existed , which corresponded to the dna nanospheres B-nanoparticle with broad size distribution . [SEP]

[CLS] in contrast , in the absence of t - dna or in the presence of background dna ( b - dna ) , no band of dna nanospheres B-nanoparticle was observed ( in the lanes x 1 + x 2 + pbs and x 1 + x 2 + b - dna in figure s1b ) , indicating that polymerization did not occur . [SEP]

[CLS] these results confirmed that t - dna specifically triggered the polymerization of x - dna into dna nanospheres B-nanoparticle . [SEP]

[CLS] the synthesized dna nanospheres B-nanoparticle were also verified by atomic B-technique force I-technique microscopy I-technique imaging ( figure s1c ) . [SEP]

[CLS] in addition , we explored the formation of dna nanospheres B-nanoparticle over time . [SEP]

[CLS] after the addition of t - dna in the mixture of x 1 and x 2 for 2 min , the band in the gel hole with strong fluorescence B-property intensity indicated that the formation of dna nanospheres B-nanoparticle started within 2 min ( figure s2 ) . [SEP]

[CLS] also , the fluorescence B-property intensity of the smear became relatively lighter over time , suggesting that the dynamic assembly of dna nanospheres B-nanoparticle continuously proceeded from 2 to 60 min . [SEP]

[CLS] for real - time monitoring of the ttp - based process , we took advantage of the quartz crystal microbalance ( qcm ) as a signal output device . [SEP]

[CLS] qcm has the ability to measure extremely small mass changes at the nanogram level by monitoring in real - time the frequency changes of quartz crystal resonator . [SEP]

[CLS] qcm , therefore , has been developed as a label - free biosensor for the sensitive analysis of biomolecules and kinetic evaluation . [SEP]

[CLS] the ttp - based system included two key stages : molecular recognition for t - dna and signal amplification by ttp ( figure s3a ) . [SEP]

[CLS] to efficiently recognize t - dna , we designed capture dna ( c - dna ) probes for complementary pairing with t - dna , which contained a thiol B-material group for immobilizing on the chip surface by au - s bond and a poly ( a ) tail for increasing the distance between the probes and chip surface and reducing the ' ' size dilemma ' ' . [SEP]

[CLS] in addition , the chip with c - dna attached was blocked by 6 - mercapto - 1 - hexanol ( mch ) to avoid non - specific adsorption . [SEP]

[CLS] in ttp - based system , the immobilized c - dna probes specifically hybridized with partial sequences of t - dna , generating a corresponding molecular recognition signal . [SEP]

[CLS] afterward , the remaining single - strand region of t - dna was exposed for subsequent signal amplification . [SEP]

[CLS] we first studied effective one - step signal amplification by the ttp system . [SEP]

[CLS] we synthesized dna nanospheres B-nanoparticle with x 1 in the periphery at a certain proportion of t - dna and x - dna , to allow their effective hybridization with t - dna ( figure s3b ) . [SEP]

[CLS] the frequency signals decreased slightly and then further decreased significantly after introducing t - dna and dna nanospheres B-nanoparticle with x 1 on the periphery , respectively ( figure s3c ) . [SEP]

[CLS] interestingly , we observed that the values of frequency changes ( df ) and rates ( ddf / dt ) both changed in the process of signal amplification relative to target recognition , owing to the introduction of dna nanospheres B-nanoparticle with high molecular weight . [SEP]

[CLS] in contrast , the frequency signal remained unchanged when applying b - dna and the following mixture of x 1 and x 2 ( figure s3c ) , confirming the high specificity of the ttp system . [SEP]

[CLS] we further developed a layer - by - layer ttp system to regulate the self - assembly of dna nanospheres B-nanoparticle that was in situ growing on qcm chip , achieving step - by - step signal amplification . [SEP]

[CLS] in detail , after the incubation B-technique of c - dna and mch , the chip was capable of t - dna - specific recognition and capture . [SEP]

[CLS] after the addition of t - dna , x 1 was introduced due to the complementary pairing between exposed sequences of t - dna and sticky end of x 1 , followed by t - dna and x 2 . [SEP]

[CLS] by the sequential injection of t - dna and x - dna as a cycle , layer - by - layer self - assembled dna nanospheres B-nanoparticle were in situ assembled on chip surface after several cycles , and consequently , ttp systems realized effective step - by - step signal amplification . [SEP]

[CLS] finally , the frequency signals were used as real - time outputs to monitor the polymerization of dna nanospheres B-nanoparticle , where df and ddf / dt reflected hybridization thermodynamic and kinetic behaviors , respectively . [SEP]

[CLS] in addition , the chip was regenerated after treatment with denaturant for the next round of testing , demonstrating the reusability and cost - effectiveness ( figure s4 ) . [SEP]

[CLS] to determine the optimal concentration ratio of t - dna to x - dna , we set three groups of experiments . [SEP]

[CLS] we defined the differences in df values between final equilibrium states and baseline as df . [SEP]

[CLS] the df values decreased twice after the introduction of t - dna and x - dna , which were recorded as df 1 and df 2 , respectively . [SEP]

[CLS] also , the values of df 2 / df 1 reflected the hybridization capacity of x - dna relative to t - dna . [SEP]

[CLS] by comparing the values of df 2 / df 1 , the concentration ratio of t - dna : x - dna at 2 : 1 had the highest hybridization capacity , which was used for subsequent experiments ( figure s5 ) . [SEP]

[CLS] after four cycles in layer - by - layer ttp system , df and dissipation change ( dd ) were clearly distinguished , demonstrating excellent capability of target recognition and signal amplification ( figure 1a ) . [SEP]

[CLS] during the first cycle , the frequency response showed a slowly decreasing trend ( from 0 hz to a8 hz ) and then a dramatic decrease ( from a8 to a31 hz ) , owing to the effective hybridization between t - dna and x 1 . [SEP]

[CLS] next , the accumulated introduction of t - dna and x - dna contributed to a multistep drop ( from a31 to a46 hz ) . [SEP]

[CLS] although the decrease after the first cycle was relatively slight due to space resistance and electrostatic repulsion , our layer - by - layer ttp system significantly improved the sensitivity of biosensor . [SEP]

[CLS] meanwhile , the corresponding mass changes were calculated by sauerbrey equation applied in aqueous solutions df = a f 3 = 2 0 ffiffiffiffiffiffiffiffiffiffiffiffiffi nr l h l pr q m q s = a cdm where f 0 is the resonance frequency of the bare resonator ; n is the number of the overtone ; r l and h l are the density and viscosity B-property of liquid , respectively ; r q and h q are the density and shear modulus of quartz , respectively ; and c is a proportionality constant according to the intrinsic parameters of the qcm device . [SEP]

[CLS] as a result there was a linear relationship between the change of mass ( dm ) and df when the flexible conformation of branched dna was ignored . [SEP]

[CLS] a gradient of mass change curve indicated the growth of dna nanospheres B-nanoparticle triggered by t - dna ( figure 1b ) . [SEP]

[CLS] we further examined the sensitivity of layer - by - layer ttp system . [SEP]

[CLS] the frequency signals were monitored in the range of t - dna concentrations from 2 pm to 0 . 2 mm , presenting a gradual increasing trend . [SEP]

[CLS] - df and the logarithmic values of t - dna concentrations showed linear relationships of y = 5 . 696x - 25 . 195 ( r 2 = 0 . 9286 ) and y = 8 . 511x - 37 . 456 ( r 2 = 0 . 9608 ) in the range of 20 pm to 20 nm , corresponding to one - cycle and threecycle amplifications , respectively ( figure s6 ) . [SEP]

[CLS] compared with the one - cycle curve , the slope of the df curve corresponding to three cycles was improved by nearly 1 . 5 times , which contributes to the effective signal amplification . [SEP]

[CLS] there existed two abnormal values : the point at 0 . 2 mm was mainly due to the complex nanostructures formed among individual dna nanospheres B-nanoparticle , resulting in the enhanced frequency signal ; the point at 2 pm was mainly due to the high background signal . [SEP]

[CLS] as a result , the limit of detection was determined as 20 pm . [SEP]

[CLS] the aforementioned results demonstrated that the ttp system worked well in laboratory - based conditions . [SEP]

[CLS] we further tested the robustness and stability of the ttp system in realistic conditions , including different temperature , ph , water B-material quality , and simulated biological fluids ( figure 2 ) . [SEP]

[CLS] we first verified that the formation of dna nanospheres B-nanoparticle was not affected in the temperature range of 4 c - 45 c by gel B-technique electrophoresis I-technique ( figure s7a ) . [SEP]

[CLS] we further tested the temperature stability ( 15 c - 45 c ) of the ttp system on qcm device . [SEP]

[CLS] the relative df showed only slight fluctuations within the temperature range of 15 c - 40 c , indicating the temperature stability of the ttp system ( figure s7b and 2a ) . [SEP]

[CLS] the signal became weaker at 45 c because of the instability of au - s bonds at a higher temperature . [SEP]

[CLS] a gradient of ph from 3 . 0 to 13 . 0 was tested . [SEP]

[CLS] the formed dna nanospheres B-nanoparticle maintained integrity in both weak acidic and weak basic buffers except for ph 3 . 0 ( figure s8a ) , which was mainly due to dna degradation induced by protonation of adenine ( a ) , guanine ( g ) , and cytosine ( c ) under strong acid condition . [SEP]

[CLS] the frequency signals were detected distinctly in solutions with different ph from 5 . 0 to 11 . 0 ( figure s8b ) . [SEP]

[CLS] in spite of the slight decrease in acidic buffers of ph 5 . 0 or in basic buffers of ph 11 . 0 , the relative df was sufficiently distinguishable for t - dna detection ( figure 2b ) . [SEP]

[CLS] we further tested the robustness of dna nanospheres B-nanoparticle in various water B-material qualities . [SEP]

[CLS] dna products formed in different environments showed obvious bands in gel holes ( figure s9 ) , which indicated that the formation of dna nanospheres B-nanoparticle was not affected by the water B-material quality . [SEP]

[CLS] the robust performance of ttp systems was also tested by qcm experiments . [SEP]

[CLS] the obtained relative df results clearly demonstrated that the ttp system performed reliably in a relatively wide range of non - laboratory water B-material environments , such as pure , river , tap , and rain water B-material ( figure 2c ) . [SEP]

[CLS] finally , to evaluate the clinical feasibility and future potentiality of ttp system , four simulated biological fluids as medium were used to assess the reliability of the ttp system , including simulated sweat , simulated urine , simulated saliva , and fetal bovine serum . [SEP]

[CLS] it was confirmed by both gel B-technique electrophoresis I-technique and frequency curves on qcm that dna nanospheres B-nanoparticle were extremely stable in various simulated biological fluids ( figure s10 ) . [SEP]

[CLS] the relative df of simulated biological fluids had slight fluctuations in the range of g20 % ( figure 2d ) . [SEP]

[CLS] according to these results , the ttp system demonstrated excellent robustness and reliability for t - dna detection in relatively harsh conditions . [SEP]

[CLS] in the aforementioned experiments , we observed that different t - dna concentrations simultaneously influenced df and ddf / dt , which corresponded to hybridization thermodynamics and kinetics , respectively . [SEP]

[CLS] we studied the thermodynamics and kinetics of dna hybridization at the biosensing interface ( figure 3 ) , by taking the first cycle of ttp system in figure s6a as an example . [SEP]

[CLS] in terms of hybrid thermodynamics , the horizontals of frequency signal curves after the addition of t - dna and x 1 ( marked by blue and red , respectively ) were set as the equilibrium states of two hybridization reactions , which reflected the termination of hybridization thermodynamics ( figure 3a ) . [SEP]

[CLS] as df was linear with dm , - df iatadna or df iax1 after the introduction of t - dna or x 1 represented the corresponding hybridization yields , where i was the concentration of t - dna . [SEP]

[CLS] the - df gradually improved linearly within a t - dna concentration range of 20 pm to 20 nm ( figure 3b ) . [SEP]

[CLS] the addition of t - dna and x 1 corresponded to the linear curves of y = 1 . 378x - 5 . 788 ( r 2 = 0 . 9558 ) and y = 4 . 318x - 19 . 407 ( r 2 = 0 . 9115 ) , respectively . [SEP]

[CLS] to clearly understand the hybridization thermodynamics , we defined r i as the hybridization capacity of x 1 to t - dna at t - dna concentrations of i . [SEP]

[CLS] showed that r i had a slight fluctuation around the value of 2 , which indicated that the hybridization capacity remained almost unchanged within a range of t - dna concentrations . [SEP]

[CLS] according to the molecular weight and concentration ratio ( 2 : 1 ) of t - dna and x 1 , we calculated the theoretical ratio of hybridization yield ðr t þ to be approximately 3 . 5 . [SEP]

[CLS] on the basis of experimental and theoretical ratio of hybridization yield , we obtained hybridization efficiency ( u i ) at different t - dna concentrations ( table s2 ) , which reached an average level of 60 % at the biosensing interface . [SEP]

[CLS] we analyzed the influencing factors for the hybridization efficiency between t - dna and x - dna in the following aspects : ( 1 ) the topologies of dna on the chip were uncontrollable , such as the influence of non - specific adsorption ; ( 2 ) the presence of spatial resistance restricted the effective binding of x - dna and t - dna ; ( 3 ) the high electron cloud density on chip surface caused electrostatic repulsion to hinder the binding of x - dna ; and ( 4 ) the x - dna was washed away before binding at a certain flow rate . [SEP]

[CLS] to sum up , hybridization efficiency could be further improved by overcoming these limitations . [SEP]

[CLS] in terms of hybridization kinetics , ddf / dt curves were drawn to display the instantaneous dna hybridization rates at different t - dna concentrations ( van der , where two peaks ( labeled by blue and red ) appeared when the introduction of t - dna and x - dna , respectively ( figure 3d ) . [SEP]

[CLS] we observed that the instantaneous hybridization rates reached a maximum shortly at the beginning of hybridization , and the polymerization lasted for a few minutes , reflecting the rapid performance of ttp system on the biosensing interface . [SEP]

[CLS] to describe the kinetic characteristics of dna hybridization , we plotted the instantaneous hybridization rates - ddf iatadna / dt and - ddf iax1 / dt corresponding to t - dna and x 1 as a function of t - dna concentrations , where i represented the concentration of t - dna ( figure 3e ) . [SEP]

[CLS] the - ddf / dt curves varied linearly within the t - dna concentration range ( 2310 a11 - 2310 a8 m ) . [SEP]

[CLS] the fitted curves were y = 0 . 1029x - 0 . 3270 ( r 2 = 0 . 9261 ) and y = 1 . 467x - 6 . 747 ( r 2 = 0 . 9076 ) , corresponding to the addition of t - dna and x 1 . [SEP]

[CLS] the slope of - ddf iax1 / dt curve was increased by 14 times to that of the - ddf iatadna / dt curve , illustrating the significantly enhanced hybridization kinetics by the ttp system owing to the introduction of x - dna with higher molecular weight . [SEP]

[CLS] we then defined ε i as the ratio of instantaneous hybridization rates to explore the concentration dependence of hybridization kinetics . [SEP]

[CLS] in figure 3f , the ε i increased first with the increase of t - dna concentration in the range of 2310 a12 to 1310 a7 m , reaching as high as 10 , and began to decrease when the t - dna concentration exceeded 10 nm , revealing an optimal kinetic concentration of 10 nm . because [SEP]

[CLS] hybridization kinetics were attributed to both mass transfer and effective collision , the ratio of hybridization rates was limited to effective collision at lower concentrations and to mass transfer at higher concentrations . [SEP]

[CLS] when t - dna was at a lower concentration , the amount of t - dna used for x 1 conjugation was limited , so as to generate a lower collision efficiency . [SEP]

[CLS] in contrast , when t - dna was at a relatively higher concentration , t - dna with higher density caused space crowding at biosensing interface , further obstructing effective mass diffusion and transfer . [SEP]

[CLS] as a result , both the limited t - dna number and the crowded space restricted the dna hybridization , leading to the lower hybridization kinetics . [SEP]

[CLS] from the above analysis , we observed that hybridization thermodynamics and kinetics exhibited different behaviors as a function of t - dna concentration . [SEP]

[CLS] hybridization thermodynamics presented concentration independence , whereas hybridization kinetics depended on the t - dna concentration owing to mass transfer and collision probability , proving guidance for the study of nucleic B-material acid I-material hybridization in interface chemistry . [SEP]

[CLS] to investigate the selectivity and specificity of the ttp system , a series of dna with non - complementary sequences ( m - dna ) were introduced including single - base and multi - base changes relative to normal dna ( n - dna ) ( table s3 ) . [SEP]

[CLS] n - dna functioned as linkers for binding two types of x - dna to generate stable dna nanospheres B-nanoparticle . [SEP]

[CLS] however , metastable dna nanospheres B-nanoparticle were produced when substituted bases existed in a sequence ( asterisk indicated substituted bases ) . [SEP]

[CLS] as the number of substituted bases increased , dna nanospheres B-nanoparticle became more unstable owing to the occurrence of bulges or mismatched bubbles , which reflected in the gradually decreased df signals ( figure 4c ) . [SEP]

[CLS] there were clearly distinguishable signals of m - dna with one to four altered bases compared with n - dna . [SEP]

[CLS] once the number of altered bases reached 4 ( including 4 , 6 , 8 and 10 altered bases ) , the frequency signals remained almost unchanged . [SEP]

[CLS] the phenomenon of sharp reduction was obviously observed from the curve of relative df ( figure 4d ) , suggesting four altered bases as the critical value of frequency signals . [SEP]

[CLS] as a result of the low binding energy , hybridization between m - dna and branched dna was difficult , showing unchanged frequency signals . [SEP]

[CLS] in addition , the intermolecular tension caused by mismatched bases also affected the base pairing . [SEP]

[CLS] interestingly , when only n - dna or m - dna was introduced , there were insignificant differences in the df signal of non - complementary sequences with altered bases of 1 , 2 , and 3 ; however , significant differences were observed after the introduction of x - dna ( figure 4d ) . [SEP]

[CLS] these results indicated that the introduction of x - dna achieved effective signal amplification and that the ttp system had a capability for the discrimination of base - changing dna from normal dna . [SEP]

[CLS] furthermore , we studied the ability of the ttp system to discriminate single - base changes at different sites in a stretch of dna . [SEP]

[CLS] to ensure that the frequency changes were only related to the locations of single - base changes , the single base was set with the same change from c to g at different locations , including m1 - m ( tg16 , middle ) , m1 - t ( tg30 , terminal ) , and m1 - i ( tg11 , internal ) . [SEP]

[CLS] these mismatched sequences with singlebase changes at different positions were clearly distinguishable from each other according to frequency signals , in which df ranked as m1 - m > m1 - t > m1 - i ( figure 4f ) . [SEP]

[CLS] the small differences produced by n - dna or single - base m - dna were amplified by the addition of x - dna , indicating that ttp - based signal amplification obviously distinguished the positions of single - base changes . [SEP]

[CLS] when altered base appeared at the location of 16 or 30 , the mismatch occurred only at the terminal of hybridization chains , which did not affect the pairing of surrounding bases . [SEP]

[CLS] however , for the altered base at the location of 11 , intermolecular mismatch caused incomplete pairing of adjacent bases due to the inherent molecular tension , even though adjacent base pairs were fully complementary ( figure 4g ) . [SEP]

[CLS] in addition , unexpected dna secondary structures also influenced the hybridization binding affinity . [SEP]

[CLS] for example , the gibbs free energy ( dg ) of m1 - i was about a4 kcal / mol when forming stable hairpin secondary structure , whereas m1 - m and m1 - t were only a0 . 44 kcal / mol ( calculated by www . nupack . org ) ( santalucia and hicks , 2004 ) . [SEP]

[CLS] as a result , the relative df of m1 - i was much smaller than that of m1 - m and m1 - t ( figure 4g ) . [SEP]

[CLS] the relative df of m - dna reflected the hybridization thermodynamics , which had a close relationship with binding energy of dna nanospheres B-nanoparticle . [SEP]

[CLS] we therefore systematically analyzed the theoretical binding energy of non - complementary sequences , including multi - base changes and single - base changes at different sites . [SEP]

[CLS] to predict the hybridization situation of target dna ( including n - dna and m - dna ) more effectively and reduce the complexity of algorithm , we reasonably simplified the dna nanospheres B-nanoparticle into a theoretical model of hybrid - dna nanostructures , as demonstrated in figure 4a . [SEP]

[CLS] we obtained the theoretical dg of hybrid - dna nanostructures ( dg h ) under the corresponding experimental conditions ( figure 4b , calculated by www . nupack . org ; . [SEP]

[CLS] the curve of relative dg h varied with the number of altered bases ( figure s11 ) , whose s - type trend was similar to the experimental results by and large . [SEP]

[CLS] however , the appearance of several abnormal points with 4 and 6 altered bases indicated that the probability of the existence of hybrid - dna was not only related to theoretical dg h . [SEP]

[CLS] we therefore introduced hybridization probability ( s ) of single - base changes ( s s ) and multi - base changes ( s m ) , which was affected by the combination of theoretical relative dg h and corresponding equilibrium yields ( q s and q m , described as q ) : s = dg h 3 q where q represented a fraction of equilibrium concentrations ( calculated by www . nupack . org ) of the expected structures to total concentrations . [SEP]

[CLS] q = equilibrium concentrations total concentrations [SEP]

[CLS] in figure 4b , q m values of m4 - dna and m6 - dna ( 0 . 314 % and 0 . 00034 % , respectively ) were dramatically lower than those of the other sequences ( m1 - dna , 99 . 3 % ; m2 - dna , 60 . 7 % ; m3 - dna , 47 . 2 % ) , indicating that the content of hybrid - dna constructed from m4 - dna and m6 - dna in solution was extremely low , which was another source of the abnormal points . [SEP]

[CLS] as a result , dg h and q m synergistically affected the probability of the existence of hybrid - dna in solution . [SEP]

[CLS] the resulting curve of s m had great agreement with the experimental results ( figure 4e ) . [SEP]

[CLS] in terms of m - dna with single - base changes at different sites , a similar phenomenon emerged . [SEP]

[CLS] the theoretical dg h was essentially consistent with the experimental frequency signals ( figure s12 ) except for the abnormal point of m1 - i . the lower q s of m1 - i ( 72 . 2 % ) relative to m1 - m and m1 - t was another primary cause of lower frequency signal . [SEP]

[CLS] as a result , the s s values of m - dna with single - base changes were in agreement with experimental values ( figure 4h ) , indicating the reliability of the theoretical model . [SEP]

[CLS] taking advantage of the established model , we predicted the hybridization probability of single - nucleotide change in long - strand dna sequences ( table s4 ) . [SEP]

[CLS] with the increase of strand length , dna sequences with single - base change tended to more occurrence of hybridization . [SEP]

[CLS] the hybridization probability reached 99 % when an altered base appeared in a stretch of 270 - bp sequences , approaching the length limit of discrimination . [SEP]

[CLS] in general , the abovementioned results showed that ttp system exhibited superior performances on the discrimination of altered dna , including the number of altered bases ( 1 - 4 nt ) and the positions of single - nucleotide changes . [SEP]

[CLS] moreover , ttp - based hybridization model effectively analyzed the hybridization probability of expected dna nanostructures , which was influenced by both binding energy and equilibrium yield . [SEP]

[CLS] to explore the fundamental reason why base - changing dna was effectively discriminated by the ttp system , we focused on the hybridization thermodynamics and kinetics in the first cycle of m - dna and n - dna in the ttp system ( figure 5a ) . [SEP]

[CLS] first , we studied the hybridization thermodynamics of m - dna . [SEP]

[CLS] as shown in figure 5b , the - df values after the addition of m - dna or n - dna and x 1 ( marked by blue and red , respectively ) reflected the corresponding hybridization yield , owing to the linearity between df and dm . [SEP]

[CLS] we observed a dramatic decline on the - df values of x 1 at the point of 4 - base change ; however , no dramatic change was observed on the - df values of m - dna or n - dna . [SEP]

[CLS] the phenomena indicated that the introduction of x 1 significantly increased the small differences of hybridization thermodynamics between m - dna and n - dna . [SEP]

[CLS] according to the theoretical hybridization yield ( r t = 3 . 5 ) calculated above , hybridization efficiencies ( u i ) of m - dna and n - dna were approximate 85 % . [SEP]

[CLS] second , we analyzed the hybridization kinetics by plotting the ddf / dt curves of m - dna and n - dna with time and the - ddf / dt values with the number of altered bases ( figures 5c [SEP]

[CLS] the ratio of the instantaneous hybridization rates of x 1 and n - dna or m - dna increased to approximately 5 times at altered bases less than 4 , demonstrating that the ttp system amplified the small differences of hybridization kinetics performance between n - dna and m - dna in an identical reaction . [SEP]

[CLS] the above analysis indicated that the differences of hybridization kinetics and thermodynamic properties are the fundamental reasons for m - dna discrimination in the ttp system . [SEP]

[CLS] single - base changes are associated with various biological and biomedical implications , such as genetic diseases , antibiotic resistance , and cancers ; the distinction of single - base changes was , therefore , important for revealing biological mechanisms and exploring the methods for disease treatment . [SEP]

[CLS] current methods for distinguishing single - base changes mainly include pcr , sequencing technology , and hybridization . [SEP]

[CLS] the traditional pcr and sequencing technology are mostly applied for distinguishing single - base changes ; however , these methods have some intrinsic disadvantages , such as time consumption , high cost , complicated operation , low specificity , and so on . [SEP]

[CLS] as a result , a large number of hybridization - based methods are developed for detecting base mutations , including protein - assistant hybridization , thermal denaturation - based hybridization , and direct hybridization . [SEP]

[CLS] protein - assistant hybridization needs to maintain enzyme B-property activity I-property during manipulating , and thermal denaturation - based hybridization needs the participation of precise temperature - control device , which undoubtedly increase the cost and difficulty of use . [SEP]

[CLS] relatively speaking , direct hybridization is the easiest way to operate . [SEP]

[CLS] our ttp system depended on the direct hybridization of nucleic B-material acid I-material , and there is no involvement of any enzyme and temperature control device , which made the operation very simple and low cost . [SEP]

[CLS] the key to direct hybridization - based methods is the hybridization design . [SEP]

[CLS] the common strategies are to design the constrained probes or to modify chemical molecules on hybridization probes . [SEP]

[CLS] relative to some constrained probes ( e . g . , hairpin probes and strand displacement probes ) and modified molecule ( e . g . , molecule beacons , artificial nucleic B-material acid I-material ) probes , ssdna as probes in our ttp system is the easiest and cheapest form . [SEP]

[CLS] moreover , the ssdna probes and x - dna amplifiers avoided the steps of toehold migration and structure de - conformation , enabling the rapid performance of the ttp system . [SEP]

[CLS] in addition , the use of qcm biosensor provided convenience for detecting singlebase changes with high specificity and selectivity , and for studying hybridization kinetics and thermodynamics of nucleic B-material acid I-material . [SEP]

[CLS] as a whole , compared with the serious drawbacks in current methods , such as complicated operation , time - consumption , high cost , and low specificity , our ttp system possessed multiple unprecedented advantages including portable design , rapid manner , robust performance , enzyme - free amplification , label - free signal readout , and labor - free usage , fully satisfying the requirements of point - of - care testing . [SEP]

[CLS] in conclusion , we proposed a branched dna - based ttp strategy for the enzyme - free and fast discrimination of base - changing dna from normal dna and developed a theoretical method for analyzing the hybridization probability of expected dna structures . [SEP]

[CLS] in ttp system , target dna triggered the self - assembled polymerization of two species of x - dna to construct dna nanospheres B-nanoparticle , realizing rapid target recognition and signal amplification for picomolar - level dna detection . [SEP]

[CLS] the formation of dna nanospheres B-nanoparticle only occurred in the presence of target dna , without the involvement of any enzymes , ensuring the specificity and simplicity of the system . [SEP]

[CLS] in addition , the ttp system exhibited excellent robustness and stability in a wide range of realistic conditions , including different ph and temperature , as well as a series of water B-material sources and simulated biological fluids . [SEP]

[CLS] furthermore , we analyzed the hybridization thermodynamics and kinetics of the ttp system at different t - dna concentrations : the hybridization kinetics depended on the t - dna concentrations , whereas thermodynamics remains almost constant , providing insight for interface chemistry . [SEP]

[CLS] significantly , the ttp system had a powerful capability of discriminating not only the number of multi - base changes but also the positions of single - base changes . [SEP]

[CLS] we proposed a theoretical model involving the synergistic effect of binding energy and equilibrium yields , based on which the hybridization probability of single - base and multi - base - changing dna was analyzed and had a quite good correlation with the experimental results . [SEP]

[CLS] we envision that our ttp system will be a powerful tool for the enzyme - free and fast discrimination of base - changing dna in poct and the theoretical analysis of nucleic B-material acid I-material hybridization . [SEP]

[CLS] we implemented a new system for the discrimination of single - nucleotide changes . [SEP]

[CLS] although our ttp system exhibited excellent robustness and stability in a wide range of realistic conditions , as well as a series s3 . [SEP]

[CLS] dna sequences of non - complementary dna with different number or positions of mismatched bases ( related to figure 4 ) . [SEP]

[CLS] real - time monitoring of layer - by - layer ttp system for step - by - step signal amplification ( a ) frequency and dissipation changes of the self - assembled dna nanospheres B-nanoparticle in the ttp system . [SEP]

[CLS] stepped frequency and dissipation change signals clearly showed the feature of layer - by - layer ttp system to form dna nanospheres B-nanoparticle via four cycles . [SEP]

[CLS] in the first cycle , a dramatic change reflected the efficient hybridization , and the accumulated introduction of t - dna and x - dna obviously increased the signals . [SEP]

[CLS] ( b ) corresponding dm of the self - assembled dna nanospheres B-nanoparticle in the ttp system calculated by sauerbrey equation . [SEP]

[CLS] the ttp system exhibited excellent robustness and reliability in relatively harsh environments ( a ) the relative df signals demonstrated the robustness of the ttp system under different temperatures ( n = 3 , mean g sd ) . [SEP]

[CLS] ( b ) the relative df signals demonstrated the robustness of the ttp system under different ph ( n = 3 , mean g sd ) . [SEP]

[CLS] ( c ) the relative df signals demonstrated the robustness of the ttp system under different water B-material environments ( n = 3 , mean g sd ) . [SEP]

[CLS] ( d ) the relative df signals demonstrated the robustness of the ttp system under different simulated biological fluids ( n = 3 , mean g sd ) . [SEP]

[CLS] ttp system showed enhanced hybridization thermodynamic and kinetic performance ( a ) the df curves changing with time . [SEP]

[CLS] ( b ) the - df curves after the introduction of t - dna ( marked with blue ) and x 1 ( marked with red ) changing with t - dna concentrations . [SEP]

[CLS] ( c ) r i reflecting dna hybridization thermodynamics , which remained constant within a concentration range of 2310 a7 to 2310 a12 m . [SEP]

[CLS] ( d ) the ddf / dt curves changing with time , reflecting instantaneous hybridization rates of t - dna with different concentrations . [SEP]

[CLS] ( e ) the - ddf / dt curves after the introduction of t - dna ( marked with blue ) and x 1 ( marked with red ) changing with t - dna concentrations . [SEP]

[CLS] ( f ) ε i increasing first and then decreasing within a concentration range of 2310 a7 to 2310 a12 m , which was limited by probe density and steric hindrance . [SEP]

[CLS] ttp system achieved the discrimination of multi - base changes and single - base changes at different locations from normal dna ( a ) the model of hybrid - dna based on the hybridization process of n - dna or m - dna ( non - complementary dna with altered bases ) with two types of x - dna . [SEP]

[CLS] ( b ) the theoretical values of binding energy and equilibrium yields . [SEP]

[CLS] ( c ) the frequency curves of base - changing dna with different number of altered bases . [SEP]

[CLS] ( d ) the relative df of base - changing dna with different number of altered bases ( n = 3 , mean g sd ) . [SEP]

[CLS] ( e ) the theoretical s m of base - changing dna with different number of altered bases . [SEP]

[CLS] the experimental results were in good agreement with the theoretical analysis . [SEP]

[CLS] ( f ) the frequency curves of base - changing dna with single - base changes at different positions . [SEP]

[CLS] ( g ) the relative df of base - changing dna with single - base changes at different positions ( n = 3 , mean g sd ) . [SEP]

[CLS] ( h ) the theoretical s s of base - changing dna with single - base changes at different positions . [SEP]

[CLS] the experimental results were good agreement with the theoretical analysis . [SEP]

[CLS] 5 . improved thermodynamic and kinetic performance by ttp system for the discrimination of m - dna and n - dna ( a ) the frequency curves of m - dna and n - dna changing with time . [SEP]

[CLS] ( b ) the - df values after the introduction of t - dna ( marked with blue ) and x 1 ( marked with red ) changing with the number of altered bases , reflecting hybridization efficiency with different number altered bases . [SEP]

[CLS] ( c ) the ddf / dt curves changing with time , reflecting instantaneous hybridization rates of m - dna with different number of altered bases . [SEP]

[CLS] ( d ) the - ddf / dt values varying with the number of altered bases , reflecting the hybridization kinetics properties of m - dna in ttp system . [SEP]

[CLS] s2 . [SEP]

[CLS] effect of reaction time on formation of dna nanospheres B-nanoparticle in ttp system [SEP]

[CLS] s10 . the simulated body fluids stability of ttp system ( related to figure 2 ) . [SEP]

[CLS] s11 . [SEP]

[CLS] the theoretical relative δg h curves of hybrid - dna with different [SEP]

[CLS] the altered base sites were marked in red . [SEP]

[CLS] the hybridization efficiency at different dna concentrations in ttp system ( related to figure3 ) . [SEP]

[CLS] dna - functionalized gold B-nanoparticle nanoparticles I-nanoparticle ( aunps B-nanoparticle ) are popular hybrid materials with applications in directed assembly , biosensor development , and drug delivery . [SEP]

[CLS] this system is particularly interesting due to the versatile optical and catalytic properties of aunps B-nanoparticle combined with the molecular recognition and programmable properties of dna . [SEP]

[CLS] instead of emphasizing applications , this review focuses on the interfaces including adsorption of thiol B-material and dna bases , colloidal stability of aunps B-nanoparticle , and related methods for preparing this conjugate . [SEP]

[CLS] the effects of salt B-material , ph , proteins B-material , and dna base composition are discussed for controlling the conformation , density , and stability of dna . [SEP]

[CLS] hybridization of dna on aunps B-nanoparticle , dna - directed growing of materials , and cellular uptake of this conjugate are discussed as examples to highlight the importance of the interfaces . [SEP]

[CLS] our understanding of these biointerfaces is still far from complete , and a few future research opportunities for engineering hybrid materials are described . [SEP]

[CLS] aside from the structural roles , certain dna sequences also carry chemical functions . [SEP]

[CLS] dna aptamers are popular ligands for molecular recognition . [SEP]

[CLS] aptamers are often around 20 - 50 nucleotides long , and aptamers for various small molecules , metal B-material ions B-material , and proteins B-material have been reported . [SEP]

[CLS] dna sequences with catalytic activities are called dnazymes , which often require metal B-material ions B-material for catalysis and are useful for metal B-material detection . [SEP]

[CLS] aptamers and dnazymes are collectively called functional dna , referring to their chemical functions . [SEP]

[CLS] compared with proteins B-material , dna has [SEP]

[CLS] conjugation of biomolecules on nanomaterials B-material has resulted in numerous hybrid materials . [SEP]

[CLS] the molecular - recognition , catalytic , and structure - directing functions of biopolymers B-material are coupled to nanomaterials B-material . [SEP]

[CLS] nanomaterials B-material in turn offer optical , electrochemical , catalytic , and magnetic B-property properties useful for sensing , diagnostics , and drug loading . among the diverse bio - nano combinations , dna - functionalized gold B-nanoparticle nanoparticles I-nanoparticle ( dna - aunps B-nanoparticle ) have played a key role in the field , and its legacy continues to date . [SEP]

[CLS] for applications , dna - aunps B-nanoparticle have been used for directed assembly of nanomaterials B-material to form random structures , colloidal crystals , and molecule - like nanoparticle B-nanoparticle oligomers . [SEP]

[CLS] in addition , various biosensors with colorimetric , fluorescence B-property , light - scattering , raman , and electrochemical detection were designed for nucleic B-material acids I-material , metal B-material ions B-material , small molecules , proteins B-material , and cells B-material . [SEP]

[CLS] finally , these conjugates have interesting applications in drug delivery . [SEP]

[CLS] many reviews have covered dna - aunps B-nanoparticle in various aspects including preparing the conjugates , sensing , directed materials assembly , and drug delivery . [SEP]

[CLS] the focus of the current review is on the biointerfaces . [SEP]

[CLS] biointerfaces often refer to the interfaces between biomaterials and biological fluids , cells B-material , or tissues . [SEP]

[CLS] in this article , we use biointerfaces to describe the dna - aunp B-nanoparticle interface and also interfacing dna - aunps B-nanoparticle with other species such as ions B-material , proteins B-material , and cells B-material . [SEP]

[CLS] sometimes , we just use ' ' interfaces ' ' in short . [SEP]

[CLS] the surface science of gold B-material has been well developed , and can be easily controlled by the self - assembled monolayer technology . [SEP]

[CLS] the interfaces between dna and aunps B-nanoparticle are critical for enabling and even driving their applications . [SEP]

[CLS] a fundamental reason is the strong interactions between dna bases and gold B-material surface . [SEP]

[CLS] our goal here is not a comprehensive review but to [SEP]

[CLS] with around 1 , 000 papers published yearly , dnafunctionalized gold B-nanoparticle nanoparticles I-nanoparticle are a useful model system for demonstrating many bionano concepts , exploring fundamental colloidal and materials science problems , and showing various practical applications in sensing , directed assembly of nanoparticles B-nanoparticle , and targeted drug and gene delivery . [SEP]

[CLS] the optical , electric , and catalytic properties of gold B-material are nicely combined with the molecular recognition , catalytic , and structure - directing properties of dna . [SEP]

[CLS] the rich interfacial interactions between dna and gold B-material , and between dna and solution components , have enabled and affected many of their properties . [SEP]

[CLS] by understanding the interfaces , more controllable , reproducible , and efficient hybrid materials can be designed and new applications envisioned to continue the legacy of this hybrid . [SEP]

[CLS] highlight representative examples to illustrate the role of interfaces . [SEP]

[CLS] we focus on the fundamental aspects of the field with the hope of obtaining a solid understanding for future research and applications . [SEP]

[CLS] with excellent plasmonic properties , aunps B-nanoparticle have extremely high extinction coefficients , allowing visual observation at low - nanomolar and even picomolar concentrations , while organic dyes need to be at micromolar concentrations to achieve the same extinction ( figure 1a ) . [SEP]

[CLS] in addition , the color of aunps B-nanoparticle can change from red to blue as the particles approach each other , allowing visual colorimetric detection ( figure 1b ) . [SEP]

[CLS] large aunps B-nanoparticle ( e . g . , > 40 nm ) strongly scatter light , while the scattering property is also significantly affected by the interparticle distance . [SEP]

[CLS] against a dark background , light scattering is also highly sensitive ( figure 1c ) . [SEP]

[CLS] aunps B-nanoparticle are strong fluorescence B-property quenchers I-property , with close to 100 % quenching efficiency for fluorophores from blue to far - red emission ( figure 1d ) . [SEP]

[CLS] adsorption of molecules may also affect the localized surface plasmon resonance ( lspr ) properties . [SEP]

[CLS] aunps B-nanoparticle can strongly enhance raman signals ( figure 1e ) , and are good conductors of electrochemical sensors . [SEP]

[CLS] small aunps B-nanoparticle act as catalysts B-property for many redox reactions ( figure 1f ) . [SEP]

[CLS] finally , aunps B-nanoparticle have high surface energy and can strongly adsorb thiol B-material , halides , and organic molecules including all the nucleotides , which in turn can alter the surface property of aunps B-nanoparticle . [SEP]

[CLS] clean gold B-material surfaces are very hydrophilic B-property but are easily contaminated in air , leading to contact angles greater than 90 . [SEP]

[CLS] aunps B-nanoparticle are dispersed in water B-material , which can protect them from airborne contamination , thus retaining a consistent surface property for a long time . [SEP]

[CLS] the most commonly used aunps B-nanoparticle for dna attachment are prepared by reducing haucl 4 with citrate , where some of the remaining citrate molecules are adsorbed on the surface ( figure 1a , the 13 - nm aunp B-nanoparticle surface ) . [SEP]

[CLS] raman signals from the au - cl bond can also be detected due to the chloride B-material used in the gold B-material source . [SEP]

[CLS] both ligands afford some negative charges for weak electrostatic stabilization , while adding salt B-material can result in aggregation of aunps B-nanoparticle . [SEP]

[CLS] some common buffers such as hepes can also strongly adsorb on aunps B-nanoparticle and affect its colloidal properties . [SEP]

[CLS] a key challenge is to retain the function of dna on gold B-material surfaces while still keeping the colloidal stability of the aunps B-nanoparticle . [SEP]

[CLS] since the invention of chemical synthesis of dna , dna oligonucleotides have become a very important biopolymer B-material in materials science . [SEP]

[CLS] during synthesis , dna can be modified at almost any position with a diverse range of functional groups . [SEP]

[CLS] the persistence length of a duplex dna is about 50 nm , corresponding to 150 base pairs , which is readily achievable by synthesis . [SEP]

[CLS] adding a base pair increases the length by 0 . 34 nm , and thus dna can be controlled with sub - nanometer precision . [SEP]

[CLS] dna is highly programmable , and many impressive nanostructures have been prepared by dna . [SEP]

[CLS] dna and functional dnamuch higher stability and is easier to modify . [SEP]

[CLS] with both structural and functional properties , dna is an ideal biopolymer B-material for materials science . [SEP]

[CLS] biointerfaces : adsorption via terminal thiol B-material and nucleobases within the context of aunps B-nanoparticle , a terminal thiol - modified dna is popular for its conjugation . [SEP]

[CLS] dna is highly negatively charged due to its phosphate backbone ( figure 2a ) , and aunps B-nanoparticle with a high density of dna layer have excellent colloidal stability by both electrostatic and steric stabilization from the dna . [SEP]

[CLS] thiolated dna has been used to functionalize au surfaces for a long time due to the high au - s affinity ( over 200 kj / mol ) , although dna desorption upon long - term storage was observed . [SEP]

[CLS] interestingly , the nature of the au - s bond is still under investigation [SEP]

[CLS] the interactions between the dna bases and aunps B-nanoparticle introduce complications . [SEP]

[CLS] all four dna bases can adsorb on aunps B-nanoparticle via the keto and imino groups ( figure 2b ) . [SEP]

[CLS] various theoretic and experimental studies indicate that adenine ( a ) has the highest affinity , thymine ( t ) has the lowest affinity , while the position of cytosine ( c ) and guanine ( g ) varies from different measurements . [SEP]

[CLS] the strength of adsorption is quite high ( e . g . , greater than 100 kj / mol for each base in vacuum ) . [SEP]

[CLS] the negatively charged phosphate backbone does not bind to the au surface , while a phosphorothioate replacing one of the nonbridging oxygen B-material atoms I-material with sulfur B-material has an affinity even stronger than the dna bases . [SEP]

[CLS] since citrate - aunps B-nanoparticle and dna are both negatively charged , their interactions are strongly affected by ionic strength , ph , and the local environment . [SEP]

[CLS] first , salt B-material is needed to screen their long - range charge repulsion to allow dna to approach aunps B-nanoparticle for adsorption . [SEP]

[CLS] adsorption of a nonthiolated dna is promoted when nacl is higher than 30 mm ( figure 2c ) , and different salts B-material have different abilities for charge screening . [SEP]

[CLS] among the group 1a metals B-material , cs + is more effective than li + in promoting the aggregation of citrate - capped aunps B-nanoparticle ( figure 2d ) . [SEP]

[CLS] this was attributed to the ability of cs + to dehydrate more easily , making it more effective in binding to the surface of aunps B-nanoparticle to decrease its negative surface potential . [SEP]

[CLS] the initial rate of dna adsorption was also faster in the presence of cs + . [SEP]

[CLS] salt B-material is also needed to achieve a high density of dna by screening charge repulsion among the dna strands on aunps B-nanoparticle . [SEP]

[CLS] interestingly , li + enabled a higher dna density than cs + , and this was attributed to the stronger binding B-event of I-event dna I-event by li + . [SEP]

[CLS] therefore , cations B-material are not simple point charges ; they can affect the dna - aunp B-nanoparticle interfaces in various ways . [SEP]

[CLS] the discussion of salt B-material is often focused on cations B-material for charge screening . [SEP]

[CLS] in fact , anions B-material are also important , mainly through their adsorption on aunps B-nanoparticle as they compete with dna adsorption . [SEP]

[CLS] for halides , their adsorption affinity on au increases with increasing halide size . [SEP]

[CLS] when the concentration of anions B-material is very high ( e . g . , reach molar concentration ) , another effect may come into play by perturbing the water B-material structure , and this is characterized by the hofmeister series . [SEP]

[CLS] discussion on this front has been limited within the context of citrate - capped aunps B-nanoparticle , since they are easily aggregated with even at moderate salt B-material concentrations ( e . g . , below 50 mm ) . [SEP]

[CLS] the solution ph is also critical for the dna - aunp B-nanoparticle system . [SEP]

[CLS] the dna bases are noncharged at neutral ph , and their ( de ) protonation takes place at around three ph units or more away from neutrality . [SEP]

[CLS] when ph is lower than 5 or higher than 9 , the dna duplex starts to destabilize . [SEP]

[CLS] adenine and cytosine can be protonated at around ph 3 , and they may neutralize the negative charges on the phosphate backbone . [SEP]

[CLS] lowering the solution ph also facilitates the formation of certain secondary structured dnas ( e . g . , i - motif , [SEP]

[CLS] parallel [SEP]

[CLS] poly ( a ) duplex , and dna triplex [SEP]

[CLS] citrate - capped aunps B-nanoparticle are quite stable between ph 5 and 9 , although citrate can be partially protonated at low ph . [SEP]

[CLS] despite the strong thiol B-material - gold B-material interaction , attachment of dna to aunps B-nanoparticle is complicated by two issues : protecting the colloidal stability of the aunps B-nanoparticle , and retaining the function of attached dna . [SEP]

[CLS] a simple mixing of dna with aunps B-nanoparticle results in adsorption of only a few dna strands with uncontrolled conformation . [SEP]

[CLS] with a high negative charge density , these adsorbed strands repel incoming dna . [SEP]

[CLS] at this moment , the adsorbed dna cannot hybridize to the cdna due to the strong interactions between dna bases and the aunp B-nanoparticle surface ( figure 3a ) . [SEP]

[CLS] by adding salt B-material to screen charge repulsion and pushing more dna strands to be adsorbed , the initially adsorbed dna bases may be displaced by the thiol B-material group of incoming dna . [SEP]

[CLS] once a high - density dna shell B-material is formed , the conjugate is highly stable and the upright dna strands are functional . [SEP]

[CLS] on a bulk planar gold B-material surface , even 1 m salt B-material can be added all at once to promote dna adsorption . [SEP]

[CLS] however , for aunps B-nanoparticle , a high concentration of salt B-material cannot be added in one shot or the aunps B-nanoparticle would aggregate . [SEP]

[CLS] the mirkin group invented the salt - aging method , whereby nacl was added at small increments ( around 10 - 50 mm each time ) . [SEP]

[CLS] after each salt B-material addition , a few more dna strands can be adsorbed , which in turn allow higher stability to withstand the addition of more salt B-material ( figure 3b ) . [SEP]

[CLS] the whole process takes more than a day to complete . [SEP]

[CLS] to retain the colloidal stability of aunps B-nanoparticle during faster salt B-material aging , surfactants B-property such as sds can be added ( figure 3c ) . [SEP]

[CLS] the resulting conjugates were given the name of spherical nucleic B-material acids I-material ( snas ) . [SEP]

[CLS] with the high curvature of small aunps B-nanoparticle , dna can be more densely packed than that on a planar gold B-material surface ( up to $ 4 - fold higher ) . [SEP]

[CLS] this very high density of highly negatively charged dna has produced many interesting properties , such as sharp melting transitions and higher affinity for its cdna . [SEP]

[CLS] at the same time , compared with free linear dna , snas have higher stability against degradation by nuclease , which was attributed to a high local ionic strength . [SEP]

[CLS] the concept of snas has been expanded beyond gold B-material cores B-material to include hollow snas , liposomal B-nanoparticle snas , and molecular snas . [SEP]

[CLS] in 2012 , we discovered that dna adsorption was significantly accelerated by lowering ph . [SEP]

[CLS] a high density of dna was attached in 3 min at ph 3 , and later it was found that poly ( a ) - containing dna is particularly attractive for this method due to formation of parallel duplex ( figure 3d ) . [SEP]

[CLS] sedighi and krull reported a facile method using positively charged magnetic B-property particles . [SEP]

[CLS] the positive surface generated a high local concentration of dna and aunps B-nanoparticle , achieving fast adsorption ( 1 , 000 - fold enhancement ) . [SEP]

[CLS] inserting an oligoethylene glycol spacer B-material between the thiol B-material group and dna also allowed rapid and quantitative attachment of the dna . [SEP]

[CLS] recently , we found that dna can be efficiently attached by simply freezing the dna and aunp B-nanoparticle mixtures , followed by thawing , with no other reagents needed ( figure 3e ) . [SEP]

[CLS] upon freezing , dna , aunps B-nanoparticle , and salt B-material were all concentrated into the micropockets between ice crystals . [SEP]

[CLS] in addition , dna oligonucleotides were aligned and stretched to expose the ends . [SEP]

[CLS] the basis of adding acids and freezing are still salt B-material related , but the stretched conformation of dna also played a critical role , allowing significantly increased kinetics of dna adsorption and retaining the upright conformation of dna at the same time . [SEP]

[CLS] to obtain aunps B-nanoparticle with a discrete number of dna strands , they were mixed at a low dna - to - aunp B-nanoparticle ratio , resulting in a poisson distribution of dna density . [SEP]

[CLS] a gel B-technique electrophoresis I-technique experiment was then performed to separate the conjugates . [SEP]

[CLS] another way to prepare dna - aunps B-nanoparticle with controlled density is using a nonthiolated diblock dna with a poly ( a ) block as an anchor . [SEP]

[CLS] the high affinity between adenine and gold B-material makes it useful for this purpose . [SEP]

[CLS] it was first realized on aunps B-nanoparticle by fan ' s group . [SEP]

[CLS] by using unmodified dna , this represents a paradigm - shifting example for making low - cost biosensing elements . [SEP]

[CLS] taking advantage of the high affinity of poly ( a ) , the density of dna is inversely proportional to the length of the poly ( a ) block ( figure 3f ) , and even monovalent dna - aunps B-nanoparticle can be achieved with this method . [SEP]

[CLS] aside from attaching simple dna oligonucleotides , structured dna such as tetrahedrons have also been immobilized on gold B-material surfaces . [SEP]

[CLS] such more rigid structures serve as a spacer B-material to maximally retain the function of biomolecules attached to it . [SEP]

[CLS] while attaching dna to aunps B-nanoparticle is well established , many other surfaces such as metal B-material oxides I-material , mos 2 , and some carbon - based materials could be difficult for covalent dna attachment . [SEP]

[CLS] interestingly , dna - aunps B-nanoparticle can strongly adsorb on all these materials to indirectly attach dna . [SEP]

[CLS] with a dense dna layer , each dna facing the material B-material can interact strongly to rival covalent B-property interactions I-property taking advantage of the polyvalent binding effect , while the dna strands away from the material B-material are still functional . [SEP]

[CLS] the ability to control the relative position of nanoparticles B-nanoparticle with sub - nanometer precision has been long desired by materials scientists . [SEP]

[CLS] dna - directed assembly can enable these applications , and aunps B-nanoparticle are always among the first materials tested for establishing these methods . [SEP]

[CLS] in this section , we outline a few important types of dna - aunp B-nanoparticle assemblies , emphasizing biointerfacial understanding . [SEP]

[CLS] in figure 4a , a and b are aunps B-nanoparticle respectively functionalized with two types of dna . [SEP]

[CLS] specific dna hybridization allows directed assembly of these aunps B-nanoparticle , accompanied with a red to blue color change . [SEP]

[CLS] the aunps B-nanoparticle , however , were randomly organized without a long - range order ( figure 4b ) . [SEP]

[CLS] it took a decade before researchers figured out a way to foster crystalline structures . [SEP]

[CLS] the flexibility of dna is critical , and the dna bonds between aunps B-nanoparticle cannot be too stable . [SEP]

[CLS] otherwise , the assembled aunps B-nanoparticle are trapped kinetically . [SEP]

[CLS] 4c shows an initial strategy by decreasing the hybridization region to 4 - 7 bp to achieve crystal - like aunp B-nanoparticle assemblies . [SEP]

[CLS] those individual weak but collectively strong short duplexes made it possible for the assembled structures to overcome the kinetically trapped states . [SEP]

[CLS] further incorporating flexible spacers B-material before the hybridization region could improve the crystal quality ( fig - ures 4d and 4e ) . [SEP]

[CLS] samples can be annealed at slightly lower than the melting temperature ( t m ) to maximize the collective interactions between sticky ends . [SEP]

[CLS] since then , by tuning the size of aunps B-nanoparticle and length of dna , numerous amounts of such colloidal crystals have been prepared . [SEP]

[CLS] some representative examples with transmission B-technique electron I-technique microscopy I-technique ( tem ) micrographs and the lattice structures are shown in figure 4f . [SEP]

[CLS] the major driving force in dna - directed crystallization is dna base pairing . [SEP]

[CLS] due to a high local dna density , snas behave dramatically differently from free linear counterparts . [SEP]

[CLS] for example , a sharp melting transition ( within a few degrees ) of dnalinked aunps B-nanoparticle is a hallmark of such materials , while free dna takes over 20 to complete melting . [SEP]

[CLS] this reflects cooperative behaviors of snas . [SEP]

[CLS] the distance between aunps B-nanoparticle also affects the stability of the assembly . [SEP]

[CLS] t m increased about 10 c after inserting an a 30 spacer B-material in the thiolated dna ( hs - dna ) , which was attributed to decreased interparticle repulsion . [SEP]

[CLS] salt B-material is important for stabilizing both dna duplexes , but the aunp B-nanoparticle assembly showed a higher t m at each salt B-material concentration . [SEP]

[CLS] overall , a high dna density on aunps B-nanoparticle resulted in a collective behavior of linked dna and stabilized the duplex . [SEP]

[CLS] snas are highly negatively charged due to the dense dna shell B-material . [SEP]

[CLS] electrostatic repulsion is expected when two snas approach each other . [SEP]

[CLS] the polymeric nature of dna also provides steric hindrance and osmotic repulsion in sna crystallization process . [SEP]

[CLS] therefore , salt B-material plays an important role in the sna crystallization . [SEP]

[CLS] to understand repulsion during sna crystallization , seo et al . investigated the gap distance ( distance between adjacent snas in crystals ) as a function of ionic strength in two systems : dna - driven and depletion - forced crystallization . [SEP]

[CLS] they found that the gap distance was a function of ionic strength , similar in both systems . [SEP]

[CLS] they concluded that the steric repulsion is the dominant repulsion force during sna crystallization . [SEP]

[CLS] more recently , they showed that a very high salt B-material concentration ( 1 m nacl ) even provided an additional repulsive force , rather than simple charge screening , resulting in larger - sized crystals . [SEP]

[CLS] modulation of dna - aunp B-nanoparticle crystals after preparing dna - aunp B-nanoparticle crystals , efforts have also been made to further modify them . [SEP]

[CLS] for example , to stabilize dna - linked crystals , mirkin and coworkers proposed a silica encapsulation method by forming a silica B-material shell I-material on preformed dna - aunp B-nanoparticle crystals ( figure 5a ) . [SEP]

[CLS] the solid superlattice exhibited higher stability toward variations in temperature , solvent , ionic strength , and pressure . [SEP]

[CLS] recently , ag + was introduced to stabilize dna - aunp B-nanoparticle crystals . [SEP]

[CLS] + was found to increase the thermal stability of duplex dna by insertion into multiple base pairs . [SEP]

[CLS] after ag metalation , the volume of the crystal contracted by 25 % . [SEP]

[CLS] the formed ag crystal showed excellent stability from ph 5 to ph 11 in various organic solvents and temperatures . [SEP]

[CLS] such high stability was attributed to the chemical bonding between ag + and dna bases . [SEP]

[CLS] superstructures of dna - aunps B-nanoparticle without linker dna assembly of dna - aunps B-nanoparticle without linker dna is also possible . [SEP]

[CLS] luo ' s group obtained monolayered dna - aunp B-nanoparticle sheets with hexagonal packing by evaporating dna - aunps B-nanoparticle in confined microholes . [SEP]

[CLS] different from base - pairing - driven crystallization , the structure was directed by nonspecific interactions between the dna layers during evaporation . [SEP]

[CLS] the interparticle spacing can be well controlled by tuning the dna length . [SEP]

[CLS] further kinetic study by small - angle x - ray scattering ( saxs ) revealed that the dna - aunps B-nanoparticle formed crystals only after a certain period of drying , suggesting a concentration threshold was needed . [SEP]

[CLS] tan et al . examined crystallization of dna ( poly - t ) - modified aunps B-nanoparticle at the air - water B-material interface using saxs and found that salt B-material concentration was critical . [SEP]

[CLS] the charge repulsion between dna - aunps B-nanoparticle prevented ordered structures when nacl was lower than 0 . 3 m , while a long - range order structure formed between 1 . 2 m and 2 . 4 m nacl . [SEP]

[CLS] interestingly the authors found that base - pairing - induced crystallization only occurred in a narrow salt B-material range ( around 0 . 3 m ) . [SEP]

[CLS] such a ' ' salting - out ' ' phenomenon of dna - aunps B-nanoparticle without linker dnas was also reported by kewalramani et al . [SEP]

[CLS] they proposed a three - stage model from gas - like to face - centered cubic crystal and then to glass - like with increasing ionic strength . [SEP]

[CLS] another direction of dna - directed assembly is to form molecule - type structures with each ' ' atom B-material ' ' being a aunp B-nanoparticle . [SEP]

[CLS] to achieve this , each aunp B-nanoparticle is often functionalized with just one or a few dna strands , which define the ' ' valency ' ' of the aunp B-nanoparticle . [SEP]

[CLS] liu and liedl reviewed dna - assembled plasmonic materials . [SEP]

[CLS] here , we emphasize the surface chemistry of tuning inter - aunp B-nanoparticle interactions . [SEP]

[CLS] alivisatos and coworkers demonstrated that single - stranded dna ( ssdna ) - linked au - ag dimers exhibited a strong color change under a dark - field microscope . [SEP]

[CLS] since ssdna is more flexible than double - stranded dna ( dsdna ) , the interparticle distance can be tuned by adjusting the ionic strength . [SEP]

[CLS] deng ' s group developed a ' ' ag + soldering ' ' strategy to stabilize the formed aunp B-nanoparticle oligomers and enhance the plasmon coupling efficiency between aunps B-nanoparticle ( figures 5b - 5d ) . [SEP]

[CLS] bis ( p - sulfonatophenyl ) phenylphosphine ( bspp ) - capped aunps B-nanoparticle modified with monovalent dna were used to form dimers , and the excess bspp on the surface served as a binding ligand for ag + ( figure 5b ) . [SEP]

[CLS] the cryo - tem images showed that the interparticle distance dropped from $ 60 nm ( figure 5c ) to $ 2 nm ( figure 5d ) after adding ag + . [SEP]

[CLS] such shortened distance also resulted in a broadened plasmon peak , which was attributed to the strong longitudinal coupling . [SEP]

[CLS] the deng group further prepared aunp B-nanoparticle dimers with strong plasmon coupling directly from bspp - capped aunps B-nanoparticle and ag + . [SEP]

[CLS] different from previous works using aunps B-nanoparticle with preloaded dnas , the investigators found that mechanically shortened fish sperm dnas could stabilize partially aggregated aunps B-nanoparticle . [SEP]

[CLS] with sub - nanometer gaps , the dimers served as an ideal substrate for surface - enhanced raman B-technique spectroscopy I-technique applications . [SEP]

[CLS] these dimers were further thermally sintered to form conductive junctions ( cj ) between aunps B-nanoparticle . [SEP]

[CLS] for 13 - nm aunps B-nanoparticle , with increased temperature , the cj distance increased from $ 7 nm to 17 nm . [SEP]

[CLS] by tuning the particle size and sintering temperature , au structures with charge - transfer plasmon over an 800 - nm range were achieved . [SEP]

[CLS] chan and coworkers demonstrated that cationic B-material polymers B-material can stabilize assembled dna - aunp B-nanoparticle superstructures by condensing the dna layers via electrostatic interactions . [SEP]

[CLS] a core - satellite superstructure was assembled based on dna - directed assembly and the conjugate was dispersed in pbs containing 0 . 01 % ( w / v ) tween 20 ( pbst ) ( figure 5e ) . [SEP]

[CLS] after adding the cationic B-material polyelectrolyte ( i . e . , poly ( allylamine ) ) , the morphology of the assembled superstructures did not change , which was also observed in silica coating B-material . [SEP]

[CLS] however , the overall size of the structure decreased from 87 to 62 nm in diameter , and a compact shell B-material was observed from the tem ( figures 5f - 5h ) , which was attributed to the condensation of dna . [SEP]

[CLS] with a more compact structure , enhanced plasmon coupling was achieved as indicated by the drastic color change after polymer B-material coating B-material ( figure 5i ) . [SEP]

[CLS] after coating B-material with the polyelectrolyte , the structure also exhibited higher stability in biological medium against endogenous nuclease - induced degradation . [SEP]

[CLS] taking advantage of the interactions between dna and metal B-material ions B-material , metal B-material oxides I-material , and metal B-nanoparticle nanoparticles I-nanoparticle , dna has been extensively used for templated growth of nanomaterials B-material . [SEP]

[CLS] some early examples relied on ag + binding to duplex dna followed by adding a reducing B-property agent I-property . [SEP]

[CLS] nam ' s group used hs - dna - modified aunps B-nanoparticle as seeds to grow au @ ag and au @ au core - shell structures ( figure 6a ) . [SEP]

[CLS] they designed a diblock dna sequence with an a 10 - peg 18 block close to the thiol B-material . [SEP]

[CLS] by optimizing the spacer B-material sequence and the amount of silver B-material - staining reagent , they were able to control the thickness of the ag shell B-material without affecting the recognition function of the other dna block . [SEP]

[CLS] by controlling the nacl concentration in the growth process , asymmetric silver B-material shells B-material were achieved . [SEP]

[CLS] control experiments showed that the dna shell B-material was particularly important , and citrate - capped aunps B-nanoparticle only form branched structures or nanoshells B-nanoparticle without gaps . [SEP]

[CLS] later , the same investigators found that the dna sequence affected the morphology of the final products . [SEP]

[CLS] while hs - poly - a - and hs - poly - c - modified aunps B-nanoparticle resulted in uniform nanogaps of $ 1 nm , hs - poly - g - and hs - poly - t - capped aunps B-nanoparticle gave nanohole - like gaps with aggregates and popcorn - like au shells B-material , respectively ( figure 6b ) . [SEP]

[CLS] using saxs , tem , and uv - visible ( uv - vis ) spectra , shen et al . examined the growth process in detail and proposed a five - stage reaction model . [SEP]

[CLS] instead of using hs - dna as capping ligands , the lu group reported nonthiolated dna to direct the growth of various metal B-nanoparticle nanoparticles I-nanoparticle on aunp B-nanoparticle seeds . [SEP]

[CLS] in an initial report , flower - like nanostructures were obtained with a 30 or c 30 , but spherical particles were formed with t 30 . [SEP]

[CLS] a 30 and c 30 adsorb on aunps B-nanoparticle more strongly compared with t 30 , suggesting that dna adsorption could direct heterogeneous growth . [SEP]

[CLS] later , a detailed study of dna - mediated growth on au nanoprisms was carried out to elucidate the role of dna sequence ( figures 6c and 6d ) . [SEP]

[CLS] in the presence of t 30 , the au seeds transformed from prisms to nonagons , hexagons , and sixpoint stars . [SEP]

[CLS] interestingly , the final products in the presence of other sequences were actually the intermediates B-property of that observed with t 30 . [SEP]

[CLS] a two - stage model was then proposed . [SEP]

[CLS] in the first stage , interaction of dna with au controls the deposition of precursors and particle growth . [SEP]

[CLS] for example , at the same dna concentration , high - affinity dnas ( poly ( a ) or poly ( c ) ) retarded the particle growth , and kinetically trapped the formed particles . [SEP]

[CLS] in the second stage , the thickness of growth was mainly controlled by the remaining precursors in the reaction solution . [SEP]

[CLS] biointerfaces in sensing aunps B-nanoparticle possess many useful signaling mechanisms ( figure 1 ) , and dna can take full advantage of the physical and chemical properties of aunps B-nanoparticle for sensing applications . [SEP]

[CLS] the related analytical biosensors need careful consideration of the surface chemistry of aunps B-nanoparticle and its interaction with dna and targets . [SEP]

[CLS] early examples demonstrated target dna - induced assembly of dna - aunps B-nanoparticle into large aggregates , resulting in a red to blue or purple color change ( figure 7a ) . [SEP]

[CLS] such aggregates possess sharp melting transitions , allowing highly selective discrimination of dna with single mismatches ( figure 7b ) . [SEP]

[CLS] the sensitivity of the assays can be enhanced by using larger particles with even higher extinction coefficients , and a 50 pm detection limit can be detected with 50 - nm aunps B-nanoparticle ( $ 1 nm detection limit with 13 - nm aunps B-nanoparticle ) . [SEP]

[CLS] due to a high local dna density , collective hybridization of dna - aunps B-nanoparticle can generate very stable assemblies . [SEP]

[CLS] with such strong interactions , even single terminal base stacking can support interparticle assembly . [SEP]

[CLS] maeda ' s group found that dna - aunps B-nanoparticle hybridized with their cdna to form aggregates at a high salt B-material concentration ( 0 . 5 m ) , but if the cdna had a terminal mismatch , the aunps B-nanoparticle remained dispersed . [SEP]

[CLS] a detailed force measurement revealed that fully hybridized dna on aunps B-nanoparticle exhibited a strong attractive force within a few nanometers , whereas dna - aunps B-nanoparticle with terminal mismatch did not show such an attraction . [SEP]

[CLS] in dna - aunp B-nanoparticle conjugates , the density and thickness of the dna layer can affect its colloidal stability . [SEP]

[CLS] when the adenosine aptamers were attached , in the absence of the target the aptamer adopted a random conformation , and the conjugate aggregated with more than 5 mm mgcl 2 ( figures 7c and 7d ) . [SEP]

[CLS] however , the conjugate remained well dispersed , even with 30 mm mgcl 2 in the presence of adenosine ( figure 7d ) . [SEP]

[CLS] it seems that the structured aptamer - target complex generated more steric repulsion to prevent aunp B-nanoparticle aggregation . it could also be that the folded aptamer disallowed interparticle dna base - pairing interactions . [SEP]

[CLS] without a thiol B-material label , dna can still adsorb on aunps B-nanoparticle via nucleobase - au interactions . [SEP]

[CLS] typically , ssdna and nonstructured dnas adsorb on aunps B-nanoparticle stronger and faster than dsdna or dna with secondary structures ( e . g . , aptamer - target complexes ) . [SEP]

[CLS] in other words , the surface of aunps B-nanoparticle is able to discriminate the folding state of probe dna . [SEP]

[CLS] this difference can be easily visualized by adding salt B-material to induce aggregation of nonprotected aunps B-nanoparticle ( figures 7e and 7f ) . [SEP]

[CLS] since the aunps B-nanoparticle do not have a dense dna shell B-material , they might aggregate because of other reasons , leading to false results . [SEP]

[CLS] for example , most of the sensing work did not consider potential interactions between the analyte and aunp B-nanoparticle surface . [SEP]

[CLS] we recently found that as ( iii ) can strongly adsorb on aunps B-nanoparticle and inhibit dna adsorption , which could cause artifacts in aptamer - based arsenic B-material detection . [SEP]

[CLS] taking advantage of the strong fluorescence B-property - quenching properties of aunps B-nanoparticle , the concept of nano - flare was proposed by mirkin and coworkers in 2007 ( figure 8a ) . [SEP]

[CLS] in their initial design , aunps B-nanoparticle ( 13 nm ) were densely functionalized with an hs - dna , which was then hybridized with a fluorophore - labeled reporter dna resulting in quenched fluorescence B-property . [SEP]

[CLS] target rna can hybridize with the probe dna and release the reporter dna with an increased fluorescence B-property signal . [SEP]

[CLS] this design was named ' ' nano - flare ' ' and has been used to detect and regulate mrna inside cells B-material ( figures 8b and 8c ) . [SEP]

[CLS] compared with the hybridization of free dna in solution , the hybridization on aunps B-nanoparticle behaved thermodynamically differently . [SEP]

[CLS] considering dna - aunps B-nanoparticle as a whole ( i . e . , snas ) , its hybridization with cdna was significantly enhanced compared with that of the free dna , with this enhancement being driven by enthalpy rather than entropy . [SEP]

[CLS] fluorescent B-property melting experiments showed that the dh of sna ( a91 . 3 g 5 . 5 kcal / mol ) was significantly more than that of linear dna ( a40 . 6 g 2 . 4 kcal / mol ) , while the entropy cost for the sna was much higher . overall , the free energy decrease upon hybridization to cdna for sna ( a15 . 5 g 0 . 2 kcal / mol ) was lower than that of a linear dna ( a13 . 4 g 0 . 1 kcal / mol ) , yielding a two - order - of - magnitude higher binding constant for sna . [SEP]

[CLS] this experiment only considered hybridization of one equivalent of cdna ( sna treated as a single entity ) . [SEP]

[CLS] further isothermal titration calorimetry experiments gave more insights into the collective behavior of the dna on sna . [SEP]

[CLS] the linear dna exhibited an expected sigmoidal 1 : 1 binding isotherm . [SEP]

[CLS] however , the sna showed a double sigmoidal binding isotherm , and the ratio was determined to be 4 and 15 , respectively . [SEP]

[CLS] by inserting a longer spacer B-material dna in the sna design , the hybridization enthalpy was close to that of the free linear dna . [SEP]

[CLS] confining dna on aunps B-nanoparticle also affects the efficiency of dna hybridization on sna . [SEP]

[CLS] sna without a spacer B-material ( i . e . , thiolated 12 - mer dna ) can only have 4 % of dna hybridized , which was 10 - fold lower than that of sna with an a 20 spacer B-material . [SEP]

[CLS] while the initial enthalpy - driven hybridization to cdna was very strong , further hybridization became progressively more difficult . [SEP]

[CLS] the melting curves showed that the dsdna on sna became less stable with increasing density . [SEP]

[CLS] the preloaded cdnas on sna generated higher enthalpy penalty for subsequent incoming cdna . [SEP]

[CLS] the hybridization kinetics were also investigated . [SEP]

[CLS] the observed rate of association ( k obs ) of linear dna in solution was 58 % of that of sna . [SEP]

[CLS] aside from simple dna oligonucleotides , functional dna such as dnazymes were also immobilized on aunps B-nanoparticle ( figure 8d ) . [SEP]

[CLS] for example , the lu group prepared uranylspecific dnazyme ( 39e ) - modified aunps B-nanoparticle ( 13 nm ) , and the fluorescently B-property labeled substrate was hybridized to the enzyme strand forming the dnazyme complex on the aunps B-nanoparticle . [SEP]

[CLS] with this nanoprobe B-nanoparticle , these authors were able to image the uranyl ion B-material ( uo 2 2 + ) in a hela cell B-material ( figures 8e and 8f ) . [SEP]

[CLS] this strategy was further modified by introducing caged dnazymes to avoid background cleavage for detection of na + in cells B-material . [SEP]

[CLS] dynamic dna networks were also designed on aunps B-nanoparticle . [SEP]

[CLS] a three - dimensional ( 3d ) dna walker was designed in which aunps B-nanoparticle were densely functionalized with short fluorophore - labeled substrates and a few long walkers ( figure 8g ) . [SEP]

[CLS] the dna walker can hybridize with the substrate and induce substrate cleavage by a nicking endonuclease , indicated by the rapid fluorescence B-property increase ( figure 8h ) . [SEP]

[CLS] in the absence of endonuclease , the fluorescence B-property increase was much slower ( figure 8i ) . [SEP]

[CLS] engineering the surface chemistry is critical for rapid dna walking . [SEP]

[CLS] li and coworkers found that threshold values exist for dna walker density with specific lengths . [SEP]

[CLS] increasing the number of walkers from 0 to 20 per nanoparticle B-nanoparticle accelerated the reaction , while a further increase to 60 decreased the signal . [SEP]

[CLS] the authors proposed that a high density of walkers would interfere with one another due to the interstrand charge repulsion and increased steric hindrance . [SEP]

[CLS] the investigators were able to detect dna targets down to 5 pm using this method . [SEP]

[CLS] sensing based on catalytic activity of aunps B-nanoparticle aunps B-nanoparticle are excellent catalysts B-property with a diverse range of catalytic activities . [SEP]

[CLS] some early applications include the use of aunps B-nanoparticle as seeds to grow large silver B-material particles for enhanced colorimetric sensing . [SEP]

[CLS] even pcr - like sensitivity was achieved with multiple stages of signal amplification . [SEP]

[CLS] using aunps B-nanoparticle to mimic enzyme - like activities has also been extensively reported , such as glucose oxidase ( gox ) and peroxidase . [SEP]

[CLS] dna adsorption may modulate such activities , allowing sensing applications . [SEP]

[CLS] for example , adsorption of ssdna and dsdna on aunps B-nanoparticle inhibited its goxlike activity by 4 - fold and 25 % , respectively . [SEP]

[CLS] since h 2 o 2 is one of the products of glucose oxidation , less h 2 o 2 was produced in the presence of ssdna , which was detected by a colorimetric assay . [SEP]

[CLS] adsorption of ssdna on the aunps B-nanoparticle would block such growth , and adding cdna forming dsdna can further recover the reaction . [SEP]

[CLS] the generated h 2 o 2 can catalyze the further growth of aunps B-nanoparticle with haucl 4 . [SEP]

[CLS] interestingly , the growth was self - limited , which could be inhibited by the adsorption of another oxidation product , gluconic acid , or due to the decreased ph . [SEP]

[CLS] dna adsorption on aunps B-nanoparticle can also alter its peroxidase - like activity . [SEP]

[CLS] based on an inhibition effect , bansal and coworkers detected kanamycin , an antibiotic compound , with high sensitivity ( limit of detection = 1 . 49 nm ) . [SEP]

[CLS] however , hizir et al . found that dna enhanced the peroxidase - like activity of aunps B-nanoparticle for a positive charged substrate , 3 , 3 0 , 5 , 5 0 - tetramethylbenzidine . [SEP]

[CLS] therefore , dna can exert a diverse range of effects , including surface blocking and electrostatic attraction of substrate , to modulate the activity of aunps B-nanoparticle . [SEP]

[CLS] biointerfaces in biomedical applications dna - aunps B-nanoparticle have been widely used in biomedical applications , including drug delivery , regulation of gene expression , and live cell B-material imaging . [SEP]

[CLS] the blood and intracellular environments are very complex . [SEP]

[CLS] since the aunps B-nanoparticle are fully shielded by the dna shell B-material , this shell B-material is the main interface within biological fluids . [SEP]

[CLS] despite being highly negatively charged , the dna - aunp B-nanoparticle conjugates are readily internalized by cells B-material . [SEP]

[CLS] the efficiency of uptake was found to correlate with the density of dna on aunps B-nanoparticle , which was attributed to the adsorption of scavenger proteins B-material leading to cellular uptake . [SEP]

[CLS] interaction of dna - aunps B-nanoparticle with serum exposure of dna - aunps B-nanoparticle to cell B-material culture media resulted in an immediate adsorption of proteins B-material , and such a protein B-material corona I-material may then alter the cellular uptake . [SEP]

[CLS] the formation of a protein B-material corona I-material was indicated by the increased hydrodynamic size and smaller negative surface charge of dna - aunps B-nanoparticle . [SEP]

[CLS] further fluorescence - based assays confirmed that each aunp B-nanoparticle ( 13 nm with 80 dnas ) can adsorb ca . 23 proteins B-material on its surface , and the number of bound proteins B-material positively correlates with the dna density . [SEP]

[CLS] the adsorption of proteins B-material on sna is sequence dependent ( figure 9a ) . [SEP]

[CLS] g - rich dna immobilized on aunps B-nanoparticle showed enhanced ability to form g - quadruplex , and the conjugates are more likely to bind with serum proteins B-material . [SEP]

[CLS] the larger hydrodynamic - sized sna with g - rich dna indicated that more proteins B-material adsorbed on the dna layer ( figure 9b ) . [SEP]

[CLS] the bicinchoninic acid ( bca ) assay also showed that poly - g - aunps B-nanoparticle adsorbed more proteins B-material ( $ 40 ) in comparison with poly - t - aunps B-nanoparticle ( figure 9c ) . [SEP]

[CLS] in addition , more types of proteins B-material were identified on the corona of poly - g - aunps B-nanoparticle , indicated by the page gel ( figure 9d ) . [SEP]

[CLS] mass spectrometric analysis showed that proteins B-material of the immune system preferentially bind to poly - g - aunps B-nanoparticle . [SEP]

[CLS] western blotting analysis was further used to analyze the adsorption of five representative proteins B-material : apolipoprotein b100 , complement factor h , transferrin , complement c3b , and serum albumin . [SEP]

[CLS] three of them , apolipoprotein b100 , complement factor h , and complement c3b , prefer poly - g - aunps B-nanoparticle . [SEP]

[CLS] interestingly , such sequence - dependent protein B-material preference only exists in the sna architecture but not in the linear form of the dna . [SEP]

[CLS] enzyme - induced dna degradation serum components ( e . g . , nucleases , biothiols ) may decrease the dna stability via displacement and / or degradation , which ultimately affects the functionality of dna - aunps B-nanoparticle inside cells B-material . [SEP]

[CLS] the integrity of dna - aunps B-nanoparticle in the presence of various nucleases has been studied . [SEP]

[CLS] the stability of dna - aunps B-nanoparticle hybridized with its cdna has a longer lifetime ( $ 100 min ) in the presence of dnase i compared with its free counterpart ( $ 23 min ) . [SEP]

[CLS] mechanistic studies showed that dnase i binds to dna - aunps B-nanoparticle stronger than to the free dna , but its cleavage of the dsdna on dna - aunps B-nanoparticle was slower . [SEP]

[CLS] the highly charged surface and high local salt B-material concentration were believed to be the major reasons for the increased stability . [SEP]

[CLS] this was also confirmed by a dna density - dependent study , in which lower dna density gave rise to shorter lifetime . [SEP]

[CLS] interestingly , an rna - dna duplex in dna - aunps B-nanoparticle degraded 2 . 5 - fold faster by ribonuclease h ( rnase h ) compared with the free duplex . [SEP]

[CLS] rnase h degrades the rna strand of the rna - dna duplex . [SEP]

[CLS] compared with dnase i , rnase h was more salt B-material tolerant , still showing activity in high kcl concentrations . [SEP]

[CLS] similar to dnase i , rnase h can bind more strongly to the rna - dna duplex on aunps B-nanoparticle than to the free duplex . [SEP]

[CLS] therefore , with retained activity on the dna - aunp B-nanoparticle surface , the high local substrate concentration and enhanced binding affinity actually promoted the rna cleavage . [SEP]

[CLS] the stability of dna - aunps B-nanoparticle in biological fluids was systematically studied by chan and coworkers , and possible pathways of degradation were investigated . [SEP]

[CLS] dna - aunps B-nanoparticle were incubated B-technique with mouse serum and the dna remaining on aunps B-nanoparticle was then analyzed . [SEP]

[CLS] first , physiological concentration of endonucleases ( e . g . , dnase i ) did not have a pronounced effect on dna - aunps B-nanoparticle , and a 500 - fold higher concentration was needed to induce obvious degradation . [SEP]

[CLS] second , these authors found that 3 0 exonuclease - induced degradation was the major pathway . [SEP]

[CLS] third , although dna may be displaced by small molecules ( e . g . , biothiols ) and proteins B-material , they pointed out most biothiols are bound to proteins B-material , and the free cysteine B-material ( 20 mm ) and glutathione ( 1 mm ) did not cause much dna desorption . [SEP]

[CLS] they proposed that proteins B-material were the major factor for dna desorption . [SEP]

[CLS] the dna desorption problem might be solved by modifying dna with multiple thiols B-material , using stronger se - au chemistry , or coating B-material aunps B-nanoparticle with a shell B-material of platinum B-material . [SEP]

[CLS] 144 [SEP]

[CLS] in 2006 , the mirkin group reported the high - efficiency cellular uptake of snas into many cell B-material lines without transfection agents . [SEP]

[CLS] the dna density is important for cellular uptake . [SEP]

[CLS] a critical dna - to - aunp B-nanoparticle ratio of $ 60 ( for 13 aunps B-nanoparticle ) is required to achieve maximal uptake . [SEP]

[CLS] zhang and coworkers recently created molecular snas with a precisely controlled number of dna strands on each polymer B-material core B-material , and found that the efficiency of cellular uptake was linearly dependent on dna density . [SEP]

[CLS] the adsorption of protein B-material was thought to enhance the cellular uptake , but adsorption of bsa or transferrin actually inhibited the cellular uptake . [SEP]

[CLS] to probe the uptake pathway of sna , patel et al . examined the effect of inhibitors on different cellular uptake mechanisms . [SEP]

[CLS] after screening several inhibitors , poly i and fucoidan were found to inhibit more than 60 % of sna uptake . [SEP]

[CLS] poly i and fucoidan are known to bind to scavenger receptors . [SEP]

[CLS] it was suggested that a high density of dna on sna surfaces behaves like polynucleotides B-material with a complex structure , which binds with scavenger receptors . [SEP]

[CLS] more specifically , the sna was internalized into cells B-material by lipid - raft - mediated rather than clathrin - mediated endocytosis B-event . [SEP]

[CLS] enzyme - linked immunosorbent assays were performed to determine the specific receptor B-material of the scavenger receptor B-material family , and the class a of sr ( sr - a ) has a high affinity with sna , with an apparent dissociation constant of $ 5 nm . this affinity is at least 10 - fold higher than that of free linear dna , highlighting the importance of multivalent interactions . [SEP]

[CLS] as described above , the dna sequence on snas affects the composition of the protein B-material corona I-material , which further affects the uptake by macrophage cells B-material . [SEP]

[CLS] while protein B-material corona I-material can form on both poly - t and poly - g snas , the latter showed much higher uptake , which was attributed to the specific adsorption of opsonin proteins B-material on the poly - g sna . [SEP]

[CLS] blocking the complement receptor B-material greatly inhibited the uptake of serum - treated poly - g sna . [SEP]

[CLS] combined with the protein B-material corona I-material analysis , they concluded that poly - g sna facilitated its internalization into macrophage cells B-material by accumulating more specific protein B-material components , which supports the binding with cell B-material - I-material surface I-material receptors I-material . [SEP]

[CLS] since 1996 , this field has been through 24 years of rapidly growing research . [SEP]

[CLS] nowadays we are seeing about 1 , 000 papers on dna - functionalized gold B-nanoparticle nanoparticles I-nanoparticle each year . [SEP]

[CLS] so far , most of the materials - related work is probably driven by curiosity , rational design , and observations . [SEP]

[CLS] it has gradually become clear that understanding the dna - aunp B-nanoparticle interfaces is critical for realizing the full potential of this conjugate . [SEP]

[CLS] all four dna bases have affinities with the aunps B-nanoparticle , and for dna to be functional , such dna base adsorption needs to be avoided . [SEP]

[CLS] for certain applications , such adsorption could also be useful . [SEP]

[CLS] we believe that dna - aunps B-nanoparticle will continue to serve as a model system for learning about bio - nano interfaces . [SEP]

[CLS] by tightly packing a high density of dna , the colloidal stability problem of the aunps B-nanoparticle can be solved . [SEP]

[CLS] at the same time , many useful properties such as tighter binding of cdna and sharp melting transitions have been observed . [SEP]

[CLS] applications in many fields were demonstrated , and we have presented examples for directed materials assembly , biosensors , and drug delivery . [SEP]

[CLS] in each case , we described important surface and interface features . [SEP]

[CLS] looking forward , there are many interesting research opportunities for this material B-material . [SEP]

[CLS] the first enabling aspect is to prepare dna - aunp B-nanoparticle conjugates . [SEP]

[CLS] so far , simple conjugation with a high density of thiolated dna is no longer a difficult task . [SEP]

[CLS] custom - designed dna - aunp B-nanoparticle conjugates are also commercially available . [SEP]

[CLS] however , preparing dna - aunp B-nanoparticle conjugates with a defined number of dna strands and functionalization of different regions of aunps B-nanoparticle with different dna sequences remains challenging . [SEP]

[CLS] it is desirable to develop simple methods to achieve these goals . [SEP]

[CLS] success in this front can enable asymmetrically assembled materials and multiplexed biosensors . [SEP]

[CLS] to achieve this goal , precise engineering of the interface is key . [SEP]

[CLS] for more complicated assembly , more purification steps are required , and the yield of the final product could be very low . [SEP]

[CLS] with this limitation , most of the work on this side is only for proof of concept . [SEP]

[CLS] on the fundamental colloid and interface science level , the role of various cations B-material , anions B-material , and important small molecules needs to be carefully studied . [SEP]

[CLS] cations B-material often act on dna , while anions B-material can compete with dna for the aunp B-nanoparticle surface . [SEP]

[CLS] small molecules may play complex roles depending on their chemical structures and charge . [SEP]

[CLS] these studies are fundamentally interesting and practically important when the materials are interfaced with practical and complex samples . [SEP]

[CLS] for the development of robust biosensors , long - term stability of the conjugate and its reproducible hybridization are very important . [SEP]

[CLS] studies have shown that the attached dna can slowly dissociate and degrade in buffer . [SEP]

[CLS] developing methods to build highly active and stable interfaces is a long - standing challenge that needs to be addressed to move the technologies from the lab to the market . [SEP]

[CLS] while enhanced stability against nucleases compared with the free dna has been shown , the difference has been quite moderate in most cases . [SEP]

[CLS] a recent report showed that nuclease degradation of dna nanostructures caused significant false positives inside cells B-material . [SEP]

[CLS] surface modification could be considered to further enhance the intracellular and plasma stability of the conjugates . [SEP]

[CLS] finally , while the formation of protein B-material corona I-material on dna - aunps B-nanoparticle has been well recognized , its effect on the target recognition of the conjugates ( e . g . , by using aptamers for targeting purposes ) needs to be systematically studied , and strategies to overcome related problems are also needed [SEP]

[CLS] attempts have been made to commercialize dna - functionalized aunps B-nanoparticle , and the most recent effort is probably by exicure to commercialize the sna technology for therapeutic applications . [SEP]

[CLS] with further understanding of biointerfaces and the intrinsic property of the conjugate , the chance of commercial success will be higher . [SEP]

[CLS] in turn , the field will benefit from commercial successes . [SEP]

[CLS] 1 . optical properties of aunps B-nanoparticle ( a ) large aunps B-nanoparticle have high extinction coefficients , ε , much higher than organic dyes . [SEP]

[CLS] ( b ) the color of aunps B-nanoparticle changes from red to blue upon aggregation . [SEP]

[CLS] ( c ) aunps B-nanoparticle can also strongly scatter light , and the scattered color is dependent on the aggregation state of aunps B-nanoparticle . [SEP]

[CLS] ( d ) aunps B-nanoparticle can strongly quench fluorescence B-property , and adsorption can also be detected by lspr . [SEP]

[CLS] ( e ) aunps B-nanoparticle can form hot spots for surface - enhanced raman B-technique spectroscopy I-technique ( sers ) . [SEP]

[CLS] ( f ) aunps B-nanoparticle can catalyze the growth of a silver B-material shell B-material and also act as oxidase or peroxidase mimics . [SEP]

[CLS] interfacing dna with aunps B-nanoparticle ( a ) a dna oligomer with four bases with a backbone phosphorothioate ( ps ) and a terminal disulfide modification . [SEP]

[CLS] the purple circles indicate the possible binding sites with aunps B-nanoparticle . [SEP]

[CLS] ( b ) binding modes and the ranking of adsorption affinity of thiol B-material , ps , and the four bases adsorbed on gold B-material surface with the structures of the bases and ps shown . [SEP]

[CLS] ( c ) kinetics of fluorescence B-property quenching by aunps B-nanoparticle as a function of nacl , indicating the dna adsorption . [SEP]

[CLS] ( d ) effect of cations B-material on aggregation of citrate - capped aunps B-nanoparticle , cs + being stronger than li + for inducing aggregation . [SEP]

[CLS] reprinted with permission from : ( c ) zhang et al . , 41 copyright 2012 , acs ; and ( d ) liu et al . , 42 copyright 2014 , acs . [SEP]

[CLS] methods for conjugating dna on aunps B-nanoparticle ( a ) a low density of dna tends to wrap around the au surface , and the dna cannot hybridize with the cdna . [SEP]

[CLS] ( b ) the typical salt - aging process involving initial dna adsorption , and gradual increase of nacl concentration . [SEP]

[CLS] ( c ) attaching dna in the presence of stabilizing ligands ( e . g . , surfactants B-property ) to improve the colloidal stability of aunps B-nanoparticle . [SEP]

[CLS] ( d ) low - ph loading requiring the dna containing a poly ( a ) block to assemble into a parallel duplex . [SEP]

[CLS] ( e ) the freezing method does not require additional reagents . [SEP]

[CLS] ( f ) anchoring poly ( a ) containing nonthiolated dna on aunps B-nanoparticle with controlled density ; a longer poly ( a ) block yields a lower dna density . [SEP]

[CLS] 4 . dna - directed assembly of aunps B-nanoparticle ( a and b ) scheme ( a ) and tem image ( b ) showing assembly of dna - aunps B-nanoparticle without crystallization . [SEP]

[CLS] aunps B-nanoparticle were modified with two different dnas , and a partial duplex linker . [SEP]

[CLS] ( c ) scheme of aunps B-nanoparticle modified with partially hybridized dna with a four - base overhang for hybridization . [SEP]

[CLS] ( d and e ) saxs pattern of dna - aunp B-nanoparticle single - crystalline domains ( d ) and the integrated data ( e ) . [SEP]

[CLS] with this design , dna - aunps B-nanoparticle formed crystallized structures ( fcc ) . [SEP]

[CLS] ( f ) different crystal structures formed by dna - aunps B-nanoparticle . [SEP]

[CLS] reproduced with permission from : ( b ) mirkin et al . , 5 copyright 1996 , springer nature ; ( d and e ) park et al . , 6 copyright 2008 , springer nature ; and ( f ) macfarlane et al . , 79 copyright 2013 , wiley - vch verlag gmbh & co . kgaa , weinheim . [SEP]

[CLS] modification B-event of dna I-event - aunp B-nanoparticle assemblies ( a ) solidifying dna - aunp B-nanoparticle crystals by a silica layer . [SEP]

[CLS] ( b - d ) scheme ( b ) showing that ag + can shorten and stabilize dna - linked aunp B-nanoparticle dimers by interacting with the surface bspp ligands . [SEP]

[CLS] the tem micrographs of the dimers before ( c ) and after ( d ) adding ag + are shown . [SEP]

[CLS] ( e - i ) enhancing the surface plasmon coupling by cationic B-material polymers B-material . [SEP]

[CLS] ( e ) a scheme showing the assembled core - satellite superstructure . [SEP]

[CLS] tem micrographs of the assembly in ( f ) pbst buffer , ( g ) with mgcl 2 , and ( h ) with a cationic B-material polyelectrolyte ( pe ) are shown . [SEP]

[CLS] ( i ) tem micrographs and photographs showing the addition of pe to the satellite - to - core B-material with increasing stoichiometry ( from 3 : 1 to 30 : 1 ) . [SEP]

[CLS] reprinted with permission from : ( a ) auyeung et al . , 84 copyright 2012 , wiley - vch verlag gmbh & co . kgaa , weinheim ; ( b - d ) wang et al . , 86 copyright 2015 , wiley - vch verlag gmbh & co . kgaa , weinheim ; and ( e - i ) chou et al . , 87 copyright 2016 , acs . [SEP]

[CLS] 6 . dna - directed growth of aunps B-nanoparticle ( a and b ) schemes ( a ) and tem micrographs ( b ) showing the growth of au shell B-material on aunps B-nanoparticle functionalized with a dense hs - dna layer of different sequences . [SEP]

[CLS] ( c and d ) schemes ( c ) and scanning electron B-technique microscopy I-technique micrographs ( d ) showing the growth on au nanoprism seeds in the presence of various dna sequences at different time points . [SEP]

[CLS] reprinted with permission from : ( a and b ) oh et al . , 99 copyright 2014 , acs ; and ( c and d ) tan et al . , 100 copyright 2015 , acs . [SEP]

[CLS] typical designs of colorimetric assays using dna - aunps B-nanoparticle ( a ) aunps B-nanoparticle are densely functionalized with hs - dna , and the target dna assembles the aunps B-nanoparticle to large aggregates with a color change . [SEP]

[CLS] ( b ) melting curves of dna without aunps B-nanoparticle ( red ) and with aunps B-nanoparticle ( black ) by monitoring the absorbance at 260 nm . [SEP]

[CLS] insets showing the derivative curve of each set . [SEP]

[CLS] ( c ) aunps B-nanoparticle are functionalized with sh - aptamer dna . [SEP]

[CLS] the target - aptamer complex can better protect the core B-material particles from salt - induced aggregation . [SEP]

[CLS] ( d ) uv - vis absorbance spectra of au - aptamer ( black ) and au - aptamer with mgcl 2 ( blue ) , and au - aptamer - target with mgcl 2 . [SEP]

[CLS] insets show images of ( 1 ) au - aptamer - target , ( 2 ) au - aptamer , ( 3 ) au - aptamer - nontarget , and ( 4 ) au - nonaptamer - target . [SEP]

[CLS] all solutions contained mgcl 2 ( 30 mm ) . [SEP]

[CLS] ( e ) nonthiolated can adsorb on aunps B-nanoparticle in the absence of targets and prevent salt - induced aggregation . [SEP]

[CLS] ( f ) uv - vis absorbance of aunps B-nanoparticle ( diamonds ) with ssdna ( circles ) , with cdna ( triangles ) , and with duplex ( squares ) . [SEP]

[CLS] inset shows the color changes of aunps B-nanoparticle - ssdna in presence of different amounts of target dna . [SEP]

[CLS] the ratio of target - to - probe dna was 0 , 0 . 2 , 0 . 4 , 0 . 6 , and 1 ( from left to right ) [SEP]

[CLS] reprinted with permission from : ( b ) elghanian et al . , 105 copyright 1997 , american association for the advancement of science ; ( d ) zhao et al . , 107 copyright 2008 , acs ; and ( f ) li et al . , 108 copyright 2004 , national academy of sciences . [SEP]

[CLS] 8 . typical designs of fluorescent B-property assays using dna - aunps B-nanoparticle ( a - c ) scheme ( a ) showing nano - flare for mrna detection . [SEP]

[CLS] a reporter dna is hybridized with dna - aunps B-nanoparticle and displaced by the target dna to produce fluorescence B-property . [SEP]

[CLS] confocal fluorescent B-property micrographs of hela cells B-material incubated B-technique with survivin nano - flare ( b ) and control nano - flare ( c ) . [SEP]

[CLS] ( d - f ) scheme ( d ) showing dnazyme - aunps B-nanoparticle for metal B-material ion B-material detection . [SEP]

[CLS] the substrate was modified with a fluorophore and optionally also a quencher . [SEP]

[CLS] confocal fluorescent B-property microscopic images of hela cells B-material treated with ( e ) or without ( f ) uranyl ions B-material and dnazyme - aunp B-nanoparticle probes . [SEP]

[CLS] the dnazyme signal is in the red channel and the nuclei are stained blue . [SEP]

[CLS] ( g - i ) 3d dna walkers ( g ) . [SEP]

[CLS] target dna unblocks the walker dna ( in blue ) , allowing its hybridization with the fluorophore - labeled substrates , which are subsequently cleaved by a nuclease . [SEP]

[CLS] a walk can induce multiple cleavage events for signal amplification . [SEP]

[CLS] kinetics of fluorescence B-property signal from dna walker ( h ) and control ( only substrate - modified aunps B-nanoparticle ) ( i ) are shown . [SEP]

[CLS] reprinted with permission from : ( b and c ) seferos et al . , 113 copyright 2009 , acs ; ( e and f ) wu et al . , 115 copyright 2013 , acs ; and ( h and i ) yang et al . , 116 copyright 2016 , acs . [SEP]

[CLS] interaction of sna with biological media scheme ( a ) showing protein B-material adsorption onto two different dna ( t - rich and g - rich ) modified aunps B-nanoparticle . [SEP]

[CLS] analysis of proteins B-material on sna after incubating B-technique in 10 % human serum for 24 h at 37 c by dynamic B-technique light I-technique scattering I-technique ( b ) , bca assay ( c ) , and page gel ( d ) . [SEP]

[CLS] reprinted with permission from chinen et al . , 138 copyright 2015 , wiley - vch verlag gmbh & co . kgaa , weinheim . [SEP]

[CLS] in a recent work published in the journal of the american chemical society , the deng group at the university of science & technology of china ( ustc ) reported the use of butanol to dehydrate gold B-nanoparticle nanoparticle I-nanoparticle / dna reaching a record high dna density of spherical nucleic B-material acids I-material ( snas ) . [SEP]

[CLS] dna - functionalized gold B-nanoparticle nanoparticles I-nanoparticle ( dna - aunps B-nanoparticle ) are critical agents in a broad range of applications from biosensing , dna - directed assembly to drug delivery . [SEP]

[CLS] when dna oligonucleotides are densely packed on aunps B-nanoparticle , such conjugates feature unique physicochemical properties such as sharp melting transitions , stronger binding B-event to I-event complementary I-event dna I-event , and highly efficient cellular uptake . [SEP]

[CLS] as such , spherical nucleic B-material acids I-material ( snas ) were used to describe these conjugates . [SEP]

[CLS] the function of snas has a lot to do with its preparation , where a thiolated dna is typically used . [SEP]

[CLS] despite the high affinity between thiol B-material and gold B-material , this conjugation reaction is complicated due to the charge repulsion between dna and aunps B-nanoparticle , as well as the colloidal stability of the aunps B-nanoparticle . [SEP]

[CLS] the classic conjugation method is called salt - aging , in which nacl is stepwise added to screen the charge repulsion and carefully avoid aunp B-nanoparticle aggregation . [SEP]

[CLS] the higher the final concentration of nacl reached , the higher dna loadings on aunps B-nanoparticle . [SEP]

[CLS] the dna strands attached at a later stage can use their thiol B-material group to displace non - specifically adsorbed dna bases from the initially attached dna , forcing the attached dna in an upright conformation . [SEP]

[CLS] to maximize dna loadings , the salt - aging process takes more than a day . [SEP]

[CLS] to shorten the aging time , surfactants B-property were used to stabilize aunps B-nanoparticle , which allowed dna loading to finish within a few hours . [SEP]

[CLS] in 2012 , our group found that at ph 3 , the reaction could be completed in minutes . [SEP]

[CLS] later , we developed a freezing method . [SEP]

[CLS] without additional reagents added , snas were prepared after freezing and thawing aunp B-nanoparticle / dna mixtures . [SEP]

[CLS] recently , deng and coworkers introduced an instant dehydration method for preparing snas and obtained conjugates with record - high dna density . [SEP]

[CLS] the dehydration - driven method has two fast solution - mixing steps ( figure 1 ) . [SEP]

[CLS] first , butanol is added to extract water B-material from the dna and aunps B-nanoparticle mixture , leading to an extremely crowded and volume - reduced dna / aunp B-nanoparticle solution . [SEP]

[CLS] it is believed that rapid thiolated dna - aunp B-nanoparticle interactions happened during this dehydration process . [SEP]

[CLS] second , concentrated snas are diluted or redispersed in an aqueous buffer for stock or use . [SEP]

[CLS] with this dehydration method , the dna ( 59 - mer ) adsorption density on each 15 nm aunp B-nanoparticle reached nearly 400 strands , which was over two to three times of that achieved by the salt - aging or freezing method based on side - byside comparisons . [SEP]

[CLS] the maximum capacity of thiol B-material groups on aunp B-nanoparticle can be estimated by assuming a typical alkythiol self - assembled monolayer structure packed on gold B-material with a footprint of 0 . 214 nm 2 . [SEP]

[CLS] on a 15 nm aunp B-nanoparticle , around 3300 alkylthiols can be adsorbed . [SEP]

[CLS] the dna density obtained from the dehy - dration method reached 12 % of this theoretical maximal capacity for alkylthiols . [SEP]

[CLS] since oligonucleotides are more bulky than simple alkyl chains , the density should be a lot lower . [SEP]

[CLS] while the absolute density may be susceptible to experimental errors , the side - by - side comparison was still impressive . [SEP]

[CLS] as such , this record - high density has broken our current understanding of snas . [SEP]

[CLS] with such a dense dna shell B-material , the snas were still functional for recognizing and hybridizing with target dna . [SEP]

[CLS] two experiments were designed to compare the performance of snas respectively prepared by the freezing and dehydration methods . [SEP]

[CLS] using a fluorescent B-property sensor based on the quenching property of aunps B-nanoparticle , greater sensitivity was observed with the sna prepared with the dehydration method . [SEP]